President Volodymyr Zelensky of Ukraine warned on Thursday that Russia was preparing a “false flag” operation to blow up a large hydroelectric dam in the south of the country, potentially flooding 80 towns, villages and cities, including the strategically important city of Kherson.

He said that the plot to attack the dam at the Kakhovka Hydroelectric Power Plant in the city of Nova Kakhovka was aimed at framing Ukraine for the devastating humanitarian and ecological disaster that would ensue. He called for the creation of an international observation mission at the plant, saying it was imperative to prevent a potential catastrophe.

“We have information that Russian terrorists mined the dam and aggregates of the Kakhovka Hydroelectric Power Plant,” he said on Thursday via video link to a meeting of European leaders in Brussels.

“The water supply to a large part of the south of Ukraine may be destroyed.”

He added that a potential attack on the dam also presented a serious security risk, because it could leave the Zaporizhzhia Nuclear Power Plant, Europe’s largest nuclear power station, without the water necessary to cool its facilities.

Water for the plant, he said, came from the Kakhovka Reservoir. Russia has not corroborated Ukraine’s claims, which could not be independently verified.

In a report, on Thursday by Tass, the Russian state news agency, Kirill Stremousov, the Moscow-backed Kherson regional deputy governor, was quoted as saying that the potential “sabotage” of the dam by Ukrainian forces would not cause a “critical” situation in the area.

A report this week from The Institute for the Study of War, the Washington-based research group, said that it appeared that Russian forces were preparing the ground to conduct a “false flag” attack on the Kakhovka Hydroelectric Power Plant.

It suggested that such an attack could be a means to distract from a potential Russian retreat from the city of Kherson, a strategically vital Black Sea port that was the first major city to fall to Russian control less than a week after the invasion.

Ukrainian forces have been advancing toward Kherson, and the recapture of the city would be a devastating blow for President Vladimir V. Putin of Russia.

New York Times News Service