At least three people were killed and 23 injured when Russia shelled elderly residents as they were being evacuated in small boats from the flooded areas in Kherson, a regional Ukrainian official said Sunday.
Ukraine alleged that Russian forces are trying to derail rescue operations.
"Today, terrorists opened fire on three boats that were used to rescue people from the flooded (eastern) bank," the Kherson region's Ukrainian-appointed governor, Oleksander Prokudin, said on Ukrainian television.
In his nightly video address, Ukrainian President Volodymyr Zelenskyy decried the Russian attacks on evacuation routes for civilians escaping the flooded areas.
"It was an evacuation from Kardashynka, a village on the left bank of Kherson region. ... The occupiers created this disaster by blowing up a dam, leaving people to their fate in flooded towns and villages, and then shelling the boats that are trying to take people away," he said.
Russian forces announced a quarantine in the Russian-occupied flooded town of Hola Prystan in the Kherson region, blocking any humanitarian aid to the people there.
"The city is blocked. The Russians closed all entrances and exits," said the head of the city's military administration, Svitlana Linnyk. "I don't yet know whether the delivery of drinking water and food will be organized."
Earlier Sunday, Ukrainian Deputy Defense Minister Hanna Maliar alleged that the Kakhovka dam was blown up by Russian forces to prevent the Ukrainian offensive in the southern Kherson region.
"By destroying the Kakhovka hydroelectric power plant, the Russian leadership is trying to divert some of the forces and resources of the Ukrainian defense forces to eliminate the man-made disaster, thereby making it impossible to liberate the occupied territories on the left bank of the Kherson region," she said on the messaging app Telegram.
Maliar added that Russia's move also intended to facilitate a deployment of Russian reserves to the Zaporizhzhia and Bakhmut areas, while preventing Ukrainian forces from freeing up reserves for a deployment to the Kherson region.
Russia has accused Kyiv of destroying the dam.
The destruction of the dam caused a vast flood inundating towns and villages. Residents are still trapped in the flooded areas while entire houses have been swept away by torrential waters.
In a tweet Sunday, Zelenskyy said that his country "will do everything to guarantee people a basis for life, even after this disaster."
Zelenskyy said that representatives of the International Court have visited the flooded area in recent days and started an investigation on what caused the collapse of the dam.
At least 700,000 people need drinking water after the collapse of the Kakhovka dam in Ukraine, United Nations Undersecretary-General Martin Griffiths said on Saturday.
The U.N. aid chief said the humanitarian situation in the country has gotten "hugely worse" since the rupture of the dam. He warned that the flooding in one of the world's most important breadbaskets will almost inevitably lead to lower grain exports, higher food prices globally and less to eat for millions in need.
Stay informed. Subscribe to our newsletter
The long-term consequences of this evolving environmental catastrophe will be generational, said Eugene Simonov, an environmental scientist with the Ukraine War Environmental Consequences Work Group (UWEC), a nonprofit organization of activists and researchers.
Simonov said fish and waterfowl that had used the Kakhovka reservoir "will lose the majority of their spawning grounds and feeding grounds."
On Friday, the Norwegian earthquake center NORSAR said that a seismological station in neighboring Romania recorded tremors in the vicinity of the dam at 2:54 a.m. Tuesday local time, around the time Zelenskyy said the breach occurred.
"What we can see from our data is that there was an explosion in the area of the dam at the same time as the dam broke," NORSAR head of research Volker Oye told The Associated Press.
The Norwegian center is part of a global monitoring system that helps verify compliance with the Comprehensive Nuclear Test Ban Treaty, the AP reported.
Ukraine counteroffensive
Ukraine said Sunday it has taken three villages in the Donetsk region.
Footage on social media showed Ukrainian soldiers hoisting the Ukrainian flag at a bombed-out building in a settlement identified as Blahodatne. The unverified video was published by Ukraine's 68th Jaeger Brigade.
Footage also showed Ukrainian soldiers celebrating in the settlement of Neskuchne, while Ukrainian Deputy Defense Minister Maliar said Ukrainian forces freed the settlement of Makarivka.
Maliar added that Ukrainian troops continued to assault Russian positions around Bakhmut.
Meanwhile, Russia claims its air defense systems shot down a Ukrainian missile near the Russian-controlled port city of Berdyansk on the Sea of Azov, Russian state-owned news agency TASS reported.
Also, Russia said Sunday it had destroyed at least seven German-made Leopard tanks and five U.S.-made Bradley vehicles over 48 hours while repelling Ukrainian attacks, though Russian bloggers reported Ukraine had briefly broken through the Russian line.
Reuters was unable to verify battlefield reports from either side.