Huge waves of water could be seen flooding the war zone after a Soviet-era dam and hydroelectric power station in Ukraine was blown up.

Mass evacuations forced residents out of their homes amid fears of widespread flood devastation. President Volodymyr Zelensky said the attack on the critical Kakhovka dam was carried out by Russia. Ukraine described it as an act of “ecocide.”

Russia likely feared that the Ukrainian army would have used the road along the top of the dam for its counteroffensive.

Video from what appeared to be a monitoring camera purported to show a number of explosions around the dam, which is in a Russian-controlled section of eastern Ukraine, while other clips show the water cascading downstream through what was left of the two-mile-long barrier.

As rescue workers rushed in to help, they were targeted by Russian artillery, hitting at least two policemen, according to Ukraine’s interior ministry.

Charles Michel, president of the European Council, said the attack on the civilian infrastructure “clearly qualifies as a war crime.”

The United Nations nuclear monitoring watchdog said there was no immediate threat to Zaporizhzhia, which is Europe’s largest atomic energy plant, but the reservoir fed by the dam is responsible for the cooling water needed to keep the nuclear site safe.

The New York Times reported that Ivan Plachkov, a former energy minister of Ukraine, warned that more than 100,000 gallons of water an hour from the reservoir was required to keep the six reactors cool and to stop the spent fuel from melting down.

Oleksandr Prokudin, the head of the Kherson Regional Military Administration, said in a video posted to Telegram it will take mere hours—within five—for the water to reach “critical levels.”

Ukrainian authorities had already warned what might happen if the dam failed: unleashing 4.8 billion gallons of water and flooding districts where hundreds of thousands of people live in what is already difficult terrain as the Russian invasion grinds on.

Residents further downstream on the Dnipro River in Kherson were warned: “Do everything you can to save your life,” according to Oleksandr Prokudin, head of Ukraine’s Kherson region military administration.

Russia’s TASS news agency says at least 300 houses in the settlements of Dnepryan and Korsunka near Nova Kakhovka could fall into the flood zone, but there are more widespread fears that hundreds of thousands of people could be displaced.

The Ukrainian Interior Ministry told residents to gather what they needed, including essential documents and pets, then turn off appliances, and flee as soon as possible.

“Russia blew up the dams,” presidential adviser Mykhailo Podolyak said in response, adding: “The purpose is obvious: to create insurmountable obstacles on the way of the advancing #AFU [the Armed Forces of Ukraine]; to intercept the information initiative; to slow down the fair final of the war.” President Zelensky described those allegedly responsible as “Russian terrorists,” adding he has convened the National Security and Defense Council for talks after the incident.

According to The Washington Post, Russian military bloggers claimed Ukraine “blew up the dam to trigger flooding that will wash away Russian positions on the left bank of Dnipro and allow a Ukrainian amphibious assault.”

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