“They decided that now, in this way, they will be able to stop the counteroffensive of Ukrainian forces,” Natalia Humeniuk, a spokeswoman for Ukraine’s southern command, told Radio Svoboda on Tuesday.
Sergei K. Shoigu, Russia’s defense minister, accused Ukraine of destroying the dam, saying Kyiv wanted to move forces and equipment defending Kherson to other parts of the front to help with its counteroffensive.
Security of the dam, a vital source of water and power, has been a continuing concern during the war, with both sides accusing the other of plotting to destroy it.
John F. Kirby, a spokesman for the National Security Council, said that the United States had been monitoring the effects of the destruction of the Kakhovka dam but that he could not confirm news reports that Russia was responsible.
Thousands of people are at risk.
Communities along the waterway are at risk of being flooded and washed away. More than 40,000 people could be in the path of flooding on both the Russian- and Ukrainian-controlled sides of the river, according to the deputy prosecutor general of Ukraine.
In telephone interviews arranged by a group distributing humanitarian aid in Antonivka, residents described how they had watched as rising waters crept from house to house. They kept their distance from the river bank, where Russian snipers on the opposite side have in the past fired at residents, they said.
The eastern bank of the river, south of the dam, is controlled by Russian forces.
The damage threatens to disrupt vital services provided by the dam’s reservoir. It will cause a severe shortage of drinking water in the Dnipro, Zaporizhzhia and Kherson regions, said Ihor Syrota, the hydropower company chief.