Battle rages in Ukraine’s southeast as Zelensky and Putin each claim the upper hand.

It was not immediately possible to confirm either side’s account of the fighting.

Though Ukraine’s battle plans target specific areas for trying to break through Russian lines, its troops are testing Russian defenses in many places for weaknesses and poor morale, and are prepared to shift position to concentrate in those areas.

The most recent battle erupted in an area of table-flat steppe in Ukraine’s south, an unforgiving landscape for war with little cover for advancing troops, where Russia has laid mine belts and dug layer upon layer of defensive trenches. Ukraine’s military and a local Russian-appointed official, Vladimir Rogov, said on Friday that heavy fighting was taking place south of the town of Orikhiv.

That area is near where military analysts have said for months that the Ukrainians might focus the brunt of a counteroffensive operation, armed with their newly acquired arsenal of Western tanks and armored personnel carriers. Kyiv’s push there, analysts say, is part of an effort to drive a wedge into land that Russia has seized since launching its full-scale invasion last year, splitting the territory into two and cutting Moscow’s supply lines to the occupied Crimean Peninsula.

Beginning on Thursday, Russian pro-war bloggers and the Russian military reported that Ukraine had unsuccessfully attempted an advance a few miles east of Orikhiv, near the village of Mala Tokmachka. Videos and photos posted by the bloggers, and verified by The New York Times, show that at least three Leopard 2 tanks and eight American-made Bradley fighting vehicles were recently abandoned by Ukrainian troops or destroyed.

Two U.S. officials, speaking on condition of anonymity to discuss sensitive military operations, said that advancing Ukrainian forces had suffered casualties, but that American assessments quantifying those losses were still being developed. The officials said that Russians had also suffered some casualties.

In most military campaigns, attacking forces typically suffer higher initial losses than dug-in defenders, and much of the terrain in Ukraine’s south is flat, open ground — leaving troops and armored vehicles exposed to enemy artillery.

The Times also verified, according to images posted by a Ukrainian brigade, that Ukrainian troops were on foot in Lobkove, a settlement west of Orikhiv, for the first time in the vicinity of the offensive. But the videos and images have emerged hours or days after they were taken, and many have come from pro-Russian sources, making it impossible to determine which side has an advantage in the fighting.

About 60 miles east of Orikhiv, Ukraine was also attacking across the plains near the town of Velyka Novosilka, where a deputy defense minister, Hanna Malyar, said on Thursday that a battle was being fought. Ukrainian officials have also said they are attacking Russian positions on the outskirts of the eastern city of Bakhmut, which fell to Russian forces last month after the longest and bloodiest battle of the war. Ukraine’s military said on Thursday that it had advanced by several hundred yards near Bakhmut.

The attack near Orikhiv is plowing directly into a dense line of Russian defenses, suggesting that Ukraine might try a direct assault on one of the shortest routes to splitting Russian-held territory. Commercial satellite images have shown multiple lines of Russian defenses in the area, where Moscow’s forces have spent months laying mine belts, digging bunkers and setting out concrete barriers for tanks.

Pentagon officials and military analysts have warned against trying to make broad assessments about Ukraine’s success based on a few days of fighting in a few locations.

“This isn’t something you judge based on a few days of fighting,” Michael Kofman, the director of Russian studies at CNA, a research institute in Arlington, Va., said in a Twitter message on Friday. “The offensive will play out over weeks and likely months.”

Christiaan Triebert and Haley Willis contributed reporting.

A top U.N. official defends the organization’s response to flooding in Ukraine.

“They’re not here,” Mr. Zelensky said in the interview with the German media outlet Bild, adding that international aid agencies were supposed to “be there first to save lives.” He traveled to the flooded areas of Kherson on Thursday to rally support and aid.

Mr. Griffiths said local Ukrainian organizations were handling nearly all the rescue and evacuation operations and aid deliveries on the front lines. Many of the local aid groups are working in partnership with the U.N. and other international aid agencies.

“This phase depends absolutely on the courage and professional capacity of Ukrainian” nonprofit groups, Mr. Griffiths said.

Mr. Griffiths said he understands and empathizes with Mr. Zelensky’s frustration but maintained that the United Nations “was getting the job done.” Drinking water remains the biggest challenge with an estimated 750,000 people lacking access to clean water, Mr. Griffiths said, raising the risk of cholera and other diseases with children and older adults being particularly vulnerable.

The U.N. said it had delivered ready to eat meals, clean water and medical kits to about 30,000 people. Two convoys had arrived in Kherson today, the U.N. said, but the situation was rapidly evolving, and the number of people at risk or in need was changing by the minute.

Mr. Griffiths said the long-term consequences of the dam collapse and flooding were “extremely dire” and would have a direct impact on global food supply because some 50,000 hectares of agriculture land were flooded and destroyed. The conflict in Ukraine, which is a major exporter of wheat and grain, has already affected the global food-supply chain, prices and security.

U.S. announces another $2.1 billion in weapons to Ukraine.

In addition to the air-defense systems and munitions, the money will be used to provide 105- and 203-millimeter artillery rounds and support for training and maintenance, the Pentagon said. Since Russia invaded Ukraine last year, the United States has committed more than $50 billion in aid to Ukraine.

American defense officials continue to emphasize air-defense systems for Ukraine, as Russia has kept up its barrages of long-range missiles at the country’s cities and infrastructure. Russia has targeted not only Ukraine’s capital, Kyiv, but also cities such as Kherson, which is in the southern area of the country and was badly hit by flooding after a dam up the Dnipro River was destroyed this week.

Ukrainian drones strike cities in Russian border, governors say.

Two other attacks were reported by the governor of the neighboring Kursk region, Roman Starovoyt. He said the Ukrainian Armed Forces had dropped an explosive device on a residential building, breaking windows, but gave no details. He also said a drone crashed at an oil depot near an airfield but didn’t damage the depot.

The New York Times could not independently confirm those claims.

In recent weeks, Ukraine has carried out several attacks in the Belgorod region with artillery and drones, forcing the evacuation of people in some border towns. Russian paramilitary groups allied with Kyiv have also mounted incursions across the border.

On June 2, Russian authorities moved about 2,500 people from communities near the border farther into Russia, underscoring how the border area has become a war zone.

Drone attacks have also been carried out in Moscow, sowing fear, and the Kremlin has accused Kyiv of being behind them. Ukraine has not claimed credit for the attacks, in keeping with the government’s general policy of remaining silent about sabotage and other attacks behind enemy lines or inside Russia.

Russia has erected by far the most fortifications in the Zaporizhzhia region, a report finds.

The number of fortifications Russia has installed in the Zaporizhzhia region since 2022 is more than double those erected in other regions of Ukraine where fighting is taking place, the report found, citing satellite data.

Zaporizhzhia has become a focal point of intensified fighting in recent days as Ukrainian forces mount an offensive that military analysts say is an effort to sever Moscow’s hold on territory connecting Russia to occupied Crimea.

The authors of the report — Seth G. Jones, Alexander Palmer and Joseph S. Bermudez Jr. — wrote that Russia’s layers of defense were designed to prevent Ukrainian troops from converging on the occupied cities of Melitopol and Berdiansk and slicing Russia’s occupied territory in two. Such a breakthrough, they said, would disrupt Moscow’s supply lines and would represent “a worst-case scenario for Russia.”

Overall, Russia’s defensive line — which stretches for about 600 miles of Ukrainian territory, according to the report — is more than double the length of the Maginot Line, the defensive barrier France erected to stop a German invasion before World War II, Mr. Jones said in an interview.

Still, Mr. Jones said, as extensive as the Russian defenses are, “there are always vulnerabilities to extensive fortifications,” especially from an attacking army, such as Ukraine’s, that is engaged in “a fight for survival.”

He expected Ukrainian forces to use drones and other technology to overcome the defenses, he said. They could also pursue sabotage behind enemy lines and make use of intelligence, partly from Western allies, to learn which parts of the fortified line were poorly constructed or weakly manned.

Satellite images suggest that at least some of the Russian fortifications are of low quality, Mr. Jones said. Some images show concrete pyramids known as “dragon’s teeth” that appear not to be connected below ground, possibly making them vulnerable to being overrun, the report found. Others sit on top of the earth, when they are supposed to be partially underground, or appear to be eroded by weather, it added.

Ultimately, Mr. Jones said, regardless of their quality, fortifications “are only as good as the forces that are defending them.”

A U.S. official says spy satellites detected an explosion just before the dam collapsed.

Seismic data picked up by the NORSAR observatory in Norway also supported the theory there had been large explosion near Kakhovka dam on Tuesday at 2:54 a.m. local time, when the structure collapsed. NORSAR said in a statement that signals captured from a station 385 miles away from the dam show clear indications of an explosion.

Engineering and munitions experts have said a deliberate explosion inside the Kakhovka dam, which is controlled by Russia, most likely caused its collapse on Tuesday. They added that structural failure or an attack from outside the dam were possible but less plausible explanations.

The administration official did not rule out the possibility that prior damage to the dam or mounting water pressure might have contributed to the collapse, but American officials believe the explosion, whether deliberate or accidental, was the likely trigger.

Experts had cautioned earlier this week that the available evidence was very limited, but they said that a blast in an enclosed space, with all of its energy applied against the structure around it, would do the most damage. Even then, they said, it would require hundreds of pounds of explosives, at least, to breach the dam.

An external detonation by a bomb or missile would exert only a fraction of its force against the dam, and would require an explosive many times larger to achieve a similar effect.

Ukraine’s intelligence agency, the SBU, says it is continuing to gather evidence to support its claim that Russia destroyed the dam. On Friday, Ukrainian intelligence released an audio recording, translated into English, that it claimed was between two Russian soldiers and was evidence that Russian forces orchestrated the destruction of the dam.

One of the speakers on the phone call says that Ukrainian forces did not cause the destruction. “It was our sabotage group,” the speaker says. “They wanted to, sort of, scare with this dam. It went not as planned, but more than they planned.”

The Ukrainians did not provide basic details that would allow independent verification of the tape, including who the participants were, why the speaker might have known what happened and why anyone might have been listening to this particular call.

Artem Dekhtyarenko, press secretary for the SBU, said in a written message that the call happened on Thursday, but that other details, such as the speakers’ locations and identities, were being withheld because “this record is an element of criminal proceedings.”

Russian officials have offered a series of different explanations for the destruction, including accusing Ukraine of sabotage, without offering evidence or explaining how Ukraine would have gained access to the dam.

Marc Santora and Gabriela Sá Pessoa contributed reporting from Kyiv.

Two are killed in Russian shelling in the flood zone, Ukrainian officials say.

Odesa residents have also reported roofs of houses, wall fragments, dead animals and even tombstones among the debris floating into the city.

Mr. Humeniuk, speaking at a news conference on Friday, said the humanitarian relief effort was being complicated by Russian forces’ direct targeting of evacuation points in the flood-stricken southern region of Kherson. She said that 20 people were injured on Thursday in a series of attacks and that Russian forces continued their bombardment at night, dropping four glide bombs on the flooded village of Beryslav.

At least two people were killed in the attacks in the Kherson region on Thursday, local officials said.

Emergency workers have enough aid supplies for the moment, she said, so Ukraine is limiting the number of humanitarian groups allowed to enter the region because of the risk of injuries from shelling that could further tax already strained medical services.

President Volodymyr Zelensky called the shelling of evacuation points, including one he visited on Thursday in Kherson, “a manifestation of evil that perhaps no terrorists in the world, except for Russian ones, have ever done.”

Mr. Zelensky also called on international aid organizations to demand that Moscow allow them to provide humanitarian assistance in flood-hit areas under the control of Russian forces. About 2,200 people have been evacuated from Ukrainian-controlled areas, according to United Nations officials, but less is known about the conditions in Russian-occupied territory.

Vladimir Saldo, the Kremlin-appointed head of the occupied part of Kherson, said on Friday that about 5,800 people had been rescued, though that figure could not be independently verified because Russia does not allow independent observers into occupied areas.

The destruction of the Russian-controlled dam early Tuesday morning unleashed torrents of water from a reservoir that held about the same volume as the Great Salt Lake in Utah, and it continued to drain on Friday. The dam is the last in a series of six that run the length of the Dnipro River, starting just outside Kyiv.

Officials at Ukrhydroenergo, the company that controlled the dam before Russian forces seized it in the first weeks of their full-scale invasion last year, said they were accumulating water in reservoirs farther upstream on the Dnipro to help ensure supplies for drinking, agriculture and other needs.

Even as floodwaters near the dam began to recede — falling by about a half-foot in Kherson by Friday morning — they are still rising further downriver. Experts said it would still be some time before the full extent of the devastation is revealed.

But Ukrainian environmental officials said the ecosystem in the vast estuary where the Dnipro River and the Black Sea meet was already ravaged. Ruslan Strilets, the Ukrainian minister of environmental protection and natural resources, said it would “be almost impossible to restore these ecosystems in their original form as created by nature.”

“And no amount of money in the world will return our unique nature to us,” he said.

Victoria Kim and Nick Cumming-Bruce contributed reporting.

Putin claims Ukrainian counteroffensive so far has failed.

Mr. Putin said it was absolutely clear that the Ukrainian counteroffensive was already underway because the Ukrainian army had begun drawing upon its “strategic reserves.” He also characterized the operations as a failure thanks to the “courage and heroism” of Russian soldiers and went into more detail than usual about the situation on the battlefield.

“Ukrainian forces haven’t achieved the goals set for them in a single combat zone,” Mr. Putin said. “That absolutely obvious.”

Still he noted that the Ukrainian military still had “offensive potential.”

The Russian leader praised the organization and management of Russian forces in response to the Ukrainian attacks as well as the effectiveness of their modern weaponry.

“Yes, we don’t have enough of those modern weapons,” he said, “but the military industrial complex of the country is developing quickly, and I am certain all the issues facing the defense sector will be solved.”

The Ukrainian government has sought to keep its plans and operations for the counteroffensive under wraps and hasn’t officially announced the start of its campaign, making it more difficult for Kyiv to deliver its narrative about what is happening on the battlefield.

Russian volunteers say they have been blocked from helping areas hit hard by dam disaster.

One of the volunteers said her team was able to travel only as far as the occupied town of Hola Prystan, to the southwest of the hardest-hit area.

Both groups said they had to hand over their donated emergency supplies, such as inflatable boats, motors and medicine, to local residents or to representatives of the Russian Ministry of Emergency Situations, who then took charge of the distribution. The groups said some affected residents were still awaiting evacuation.

Volunteers have created an open-source digital map with locations of residents who have requested help in online chat groups set up to coordinate aid efforts. It is unclear whether the volunteers have been able to deliver the aid directly.

In the absence of independent observers, reports about the aftermath of the disaster in the occupied territory has come mainly from Russian authorities, who have largely portrayed the flooding as a serious but manageable emergency.

“We have all the needed resources and material,” the deputy chief of Russia’s emergency response agency, Anatoly Suprunovsky, told the country’s Interfax news agency on Thursday.

He said 14,000 homes had been damaged by the flooding, while Russia’s state-run Tass news agency on Friday put the figure at 22,000 homes.

Russia’s governor of the occupied part of the Kherson region, Vladimir Saldo, said on Friday that eight people had died from the flooding in the territory under his control. In contrast to the federal agencies, he called the situation “catastrophic.”

Ukraine has not provided a death estimate for the territory under its control. Natalia Humeniuk, a spokeswoman for Ukraine’s southern military command, said Friday that the Ukrainian military was assisting in the evacuation of occupied territories but declined to provide details, citing operational security.

Russian state television programs have broadly played down the humanitarian toll of the dam explosion, focusing instead on laying the blame on the Ukrainian government and emphasizing the negative consequences of the disaster for Kyiv. On Friday, for instance, Russia’s Channel One dedicated only about 30 seconds of its 16-minute flagship morning news program to the Kherson flooding.

Marc Santora and Oleg Matsnev contributed reporting.

A drone factory that Iran is helping Russia build could be operational next year, the U.S. says.

Plans for the plant have been known for some time. The Wall Street Journal reported plans for a potential drone factory in Yelabuga in February, and the White House released a satellite image of the factory’s intended site that was dated in early April.

An examination of satellite imagery by The New York Times shows a series of new buildings constructed in the industrial area since 2021. Construction on the buildings highlighted by the White House in the declassified intelligence started at the end of January 2021, and a small structure was recently added, the Times review showed.

By releasing the declassified information, American officials are trying to raise the pressure on Iran and make it more difficult to complete the work. On Friday, Mr. Kirby also said the United States would release a new advisory intended to help businesses around the world ensure that “they are not inadvertently contributing” to Iran’s drone program.

A key part of America’s strategy for helping Ukraine is to prevent Russia from gaining access to new military equipment or rebuilding its depleted stocks. And hindering trade between Russia and Iran is one of the most important elements of that effort.

Currently, according to the White House, Russian ships transport drones from Amirabad, Iran, across the Caspian Sea to Makhachkala, Russia. From there, they are transported to two bases: one northeast of Ukraine and one east of Ukraine. They are then used to attack Ukrainian targets.

Mr. Kirby said the arms trade between Iran and Russia was flowing both ways.

“Russia has been offering Iran unprecedented defense cooperation, including on missiles, electronics and air defense,” he said, adding that Iran had finalized a deal to buy Su-35 fighter jets from Russia and was seeking attack helicopters, radars and combat trainer aircraft.

Washington believes that the drone purchases are violations of United Nations Security Council resolutions and has imposed sanctions on Iranian companies involved in designing, building and transporting the drones.

Mr. Kirby described the cooperation between Iran and Russia as “a full-scale defense partnership that is harmful to Ukraine, to Iran’s neighbors and to the international community.”

Sweden says it will allow NATO troops on its soil even before it joins the alliance.

Sweden applied last year to join NATO as a result of Russia’s invasion of Ukraine. Objections from Turkey and Hungary have delayed the bid, and Sweden now hopes to join before a NATO summit in Lithuania next month.

A senior NATO-country ambassador said there was more confidence now that President Recep Tayyip Erdogan of Turkey, just re-elected for another five-year term, would support Sweden’s membership.

Turkey’s new foreign minister spoke to his Swedish counterpart on Wednesday. And next week, Jens Stoltenberg, the alliance’s secretary general, will meet with representatives of Finland, Sweden and Turkey.

Mr. Stoltenberg has said that Sweden has fulfilled Turkey’s demands, but Mr. Erdogan blocked Sweden’s membership during his re-election campaign, arguing that Stockholm has not done enough to fight terrorism — especially from the Kurdistan Workers’ Party, or P.K.K., which the United States and the European Union consider a terrorist group — and that it has not extradited some people Turkey wants.

But Sweden has in the last year amended its Constitution and toughened its antiterrorism law, which went into effect on June 1. It has also lifted an embargo on arms sales to Turkey.

In addition, the Swedish high court this week ruled that the government can extradite a Kurd who Turkey says is a supporter of the P.K.K. and is wanted in Turkey. The man, Mehmet Kokulu, was convicted in 2014 in Turkey for cannabis possession and was sentenced to four years and seven months in prison. After his release on parole, he legally traveled to Sweden in 2018, but Turkey has demanded his extradition, saying that he must complete his prison sentence there.

Should the optimism about Sweden prove accurate, Hungary is also expected to go along with ratifying Swedish NATO membership.

As negotiations among NATO allies continue before the Vilnius summit meeting next month, officials say there is a growing consensus that Denmark’s prime minister, Mette Frederiksen, could succeed Mr. Stoltenberg at the helm of the alliance. Ms. Frederiksen, 45, would be the first woman to hold the post and recently returned from a trip to Washington, where on Tuesday she met President Biden and other officials whose support would be vital.

A Social Democrat, she has been Denmark’s prime minister since 2019 and has promised to increase the country’s military spending to reach NATO’s target of 2 percent of economic output.

A senior NATO official said that France and others were insisting that a new secretary general come from a country that is part of the European Union, which would rule out Britain’s defense secretary, Ben Wallace, who has expressed interest in the job.

There is also the view, the official said, that candidates from Central Europe and the Baltics are too closely associated with an aggressive stance on Russia and rapid Ukrainian membership of the alliance to be able to achieve consensus. All 31 NATO countries must agree on a new secretary general.

Biden and Sunak vow that their countries will continue to support Ukraine.

Mr. Biden said he was confident that he could persuade a divided Congress to support a new round of funding for Ukraine, though he would not put a dollar amount on the package.

“I believe we’ll have the funding necessary to support Ukraine as long as it takes,” Mr. Biden said, adding that the “vast majority” of his critics in Congress would agree that funding Ukraine would be better than allowing Russia to go unchecked.

The Kakhovka dam’s destruction isn’t expected to affect Ukraine’s counteroffensive.

“This will have a certain impact as the landscape of the future battlefield has changed significantly and even the front line itself has changed,” Natalia Humeniuk, a spokeswoman for Ukraine’s southern military command, told local news outlets. “But this is not a critical change.”

The military had planned for the possibility that Russia would blow up the dam, she added. President Volodymyr Zelensky of Ukraine has warned of the same.

The flood will have little effect on Ukraine’s counteroffensive, as its military never intended to make fighting along the river a major part of the overall campaign, Mykhailo Samus, a director of the Army, Conversion and Disarmament Center in Kyiv, said in a telephone interview.

Ukraine’s threats of a riverine assault were designed to force Russia to deploy troops away from the main area of attack, he said.

“Before the flood we needed to cross the Dnipro and after the flood it is the same, just harder,” he said. “Auxiliary and diversionary maneuvers can still be conducted.”

In a call, Putin and the leader of South Africa affirm diplomatic ties and talk Ukraine.

Both leaders issued statements on Wednesday night, after the call.

The leaders’ discussions focused on a planned African peace mission to Moscow and Kyiv, in a bid to facilitate negotiations, both statements said. Mr. Putin said he would welcome the delegation of African heads of state.

Last month, Mr. Ramaphosa announced a “peace mission” that would include leaders from Egypt, the Republic of Congo, Senegal, Uganda and Zambia. It is unclear when the trip will take place.

Mr. Ramaphosa said President Volodymyr Zelensky of Ukraine welcomed the initiative over a phone call last month. But Mr. Zelensky has made clear that he would reject any calls for peace talks that do not include a demand that the Russian military first withdraw from all of Ukraine’s territory, and Mr. Putin has shown no signs of wanting to make concessions.

In their call, Mr. Putin and Mr. Ramaphosa also discussed the second Russia-Africa summit, to be held in St. Petersburg in July, and the gathering of BRICS nations — Brazil, Russia, India, China and South Africa — in August, the statements said.

Mr. Putin’s expected attendance at the BRICS summit in South Africa has become an increasing source of global tension. Mr. Ramaphosa faces growing international and domestic scrutiny over whether his country, a member of the International Criminal Court, would arrest Mr. Putin and hand him over to the court.

In March, the court, in The Hague, issued an arrest warrant over charges linked to Mr. Putin’s role in the abduction and deportation of Ukrainian children. The warrant has forced Russia’s allies who are also members of the court, to decide whether they would host Mr. Putin on state visits.

South African officials, mindful of their relations with Russia, have said they are seeking legal advice in weighing their obligations to the international court.

The United States has criticized South Africa over its warm relations with Moscow, while Mr. Ramaphosa has said his country has been facing enormous pressure to abandon its policy of nonalignment in the face of Russia’s war against Ukraine.

Last month, the United States ambassador to South Africa accused the South African government of providing weapons and ammunition via a Russian ship that was allowed to dock in a South African naval base last December. South African officials said they would investigate the accusations.

News media in South Africa and Britain have reported that South African officials are considering moving the BRICS summit to a country that is not a signatory of the court, to avoid the diplomatic headache. During his visit to South Africa last week, Sergey V. Lavrov, the Russian foreign minister, dismissed the reports. South Africa’s foreign minister, Naledi Pandor, would not comment on the reports, or on the arrest warrant for Mr. Putin.

Ukraine’s charities, hardened by war, respond quickly to the flooding.

It is not just the people who have proved resilient.

Ukraine’s transport infrastructure has also held up during the conflict, despite many direct attacks in it — and transportation can be a critical factor in any disaster response. When the Nova Kakhovka dam was breached on Tuesday, the government was able to evacuate people from the flood zone to the city of Mykolaiv by rail.

“Local civil society, authorities, the private sector — these things are underestimated in a crisis,” said Jan Egeland, the secretary general of the Norwegian Refugee Council and a former United Nations humanitarian coordinator. “They are the first on the spot.”

Ukraine, Mr. Egeland said, has “more logistics, more trained personnel and more available in the market” for aid work.

On Thursday, the country’s president, Volodymyr Zelensky, called for a bigger global response to the destruction of the dam, which sent water from a reservoir cascading downstream. To date, the United Nations has distributed more than 100,000 bottles of water and provided food aid to 18,000 people and cash assistance to 3,500 people, according to Jens Laerke, a spokesman for its Office for the Coordination of Humanitarian Affairs.

Conducting evacuations and providing clean water are among the most pressing needs in the flood zone, but the task has been complicated. Russian forces on the east bank of the Dnipro are still shelling areas under Ukrainian control. And there has also been unwillingness from some residents, who endured months of occupation followed by months under attack, to depart.

Selena Kozakijevic, the Ukraine area manager for CARE, the international aid organization, said that many of those who live near the river bank were old and experienced ill health and disabilities.

“Many are still refusing to leave their homes, even if they are flooded,” she said. “This is a population that has been there since the start of the conflict.”

Even after the flooding subsides, people who choose to remain may face other risks for months or years, including from polluted water and land mines that have drifted from their original positions.

Ukrainian aid groups, as well as most international humanitarian organizations working in Ukraine, are staffed primarily with nationals who have the advantage of speaking the language, understanding the country and often knowing the affected locality intimately.

Ukrainian responders from the immediate vicinity, however, often face the additional challenge of being caught up in the very disaster to which they are responding.

Even the best-prepared countries often struggle to manage major disasters alone, Mr. Egeland said. He cited Turkey as an example of a country with a strong emergency preparedness sector that was nevertheless hard pressed to deal with the aftermath of an earthquake in February that killed nearly 60,000 people.

Much comes down to money.

Countries hit by disaster need financial aid both to tackle the immediate crisis and then to provide long-term support. In this respect, the international visibility that war has already brought to Ukraine has made it easier for aid groups to raise funds.

In a bid to draw attention to other crises in which large numbers of people have been forced from their homes, the Norwegian Refugee Council last week published a list of the world’s 10 most neglected displacement crises. All 10 countries were in Africa or Latin America, with Burkina Faso at the top of the list.

‘It is apocalyptic, but we are alive’: A Kherson resident says he has no intention of leaving.

While the family home may have been spared, he said that the floods had completely submerged his 8-year-old vintage clothing business across town.

“Everything is gone; I am exhausted,” he said.

Over the past two days, Mr. Boyko said, he had rushed to help desperate neighbors who were retrieving belongings from flooded homes in the town of Antonivka — about 10 minutes up the river from Kherson’s city center. He said he had been caring for scores of animals across Kherson left behind by fleeing residents.

Mr. Boyko’s home lost electricity and gas in the flooding, and shelling has resumed in the evenings. But he said he now had no intention of leaving.

“It is a new challenge, but we are well-practiced in crisis,” he said. “Besides, who will care for all the animals in this city when I leave?”

Kherson is hit by Russian shelling hours after a Zelensky visit.

Nine people were injured in the shelling near the evacuation point, among them one policeman, one emergency worker and one volunteer from Germany, according to Oleksandr Prokudin, the head of Kherson regional military administration.

The explosions hit at around 2 p.m. local time. “Leave, leave,” one man shouted, according to a witness. A young man held a bandage on the wounded head of an older man, and blood dripped down the younger man’s arm as he tried to offer words of comfort, witnesses said.

Serhiy Ludensky, a volunteer from an animal care center, was on a boat near Ship Square when the shelling hit a building close by, he said. He said he could hear people screaming. “There was nowhere to hide,” he said. The people on the boat managed to break down the door of a flooded building to wait for the explosions to stop.

Kristina Berdynskykh, a journalist from Kherson, had just finished an interview with a 14-year-old boy who escaped from occupied territory by boat with five members of his family, when the first explosions echoed over the waters.

“We just tried to hide by the nearest wall, but someone told us it is unsafe and we should move to another place, and I began to run to my colleagues from other media,” she said. They finally found a building they could hide in for more than 30 minutes before they emerged.

Ship Square was one of several areas in the city of Kherson targeted by the Russian forces on Thursday, according to Ukrainian officials and witnesses.

Ukrainian officials accused Russian soldiers of opening fire on people trying to evacuate from the flooded city of Oleshky, which lies on the Russian-controlled eastern bank of the Dnipro River.

A New York Times photographer was on a boat in the flooded Korabel neighborhood of the city when he saw at least two waves of shelling hit nearby, around 10 minutes apart. The second attack hit a barge near a bridge that links the island neighborhood with the mainland.

Brendan Hoffman contributed reporting.