Ukrainian President Volodymyr Zelenskiy described the breach of the Kakhovka dam in southern Ukraine as "an environmental bomb of mass destruction" as a Ukrainian official and the United Nations warned that it could spark an environmental disaster.
The breach of the Russian-held Soviet-era dam in the early hours of June 6 unleashed a torrent of water that flooded villages and sparked the evacuation of tens of thousands of people.
"Such deliberate destruction by the Russian occupiers and other structures of the hydroelectric power station is an environmental bomb of mass destruction," Zelenskiy said in his nightly video address.
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Zelenskiy said Russia deliberately carried out the attack on the dam but said it will have no effect on Ukraine's ability to recapture its own territory.
The UN’s humanitarian agency said it was gravely concerned about the destruction "and the severe humanitarian impact on hundreds of thousands of people on both sides of the front line."
Authorities said people had been evacuated from areas threatened by massive flooding downstream in the Kherson region as water levels rose by up to 12 meters in some areas, and Russian authorities in occupied southern Ukraine declared a state of emergency. Neither side reported any deaths or injuries.
"The Kakhovska [dam project] has actually been destroyed, it's hard for me to imagine whether it will be possible to do something with it once the war has ended. The destruction is of such a scale that a lot of water will come out and there will be flooding, especially in the old part of the city," said Nova Kakhovka Mayor Volodymyr Kovalenko.
Oleksiy Kuleba, deputy head of Ukraine’s presidential office, said the destruction of the dam will cause a large ecological problem, noting that more than 400 tons of lubricating oil had been stored in tanks at the Kakhovka hydro power plant.
"We cannot be sure yet what amount has already ended up in the Dnieper River, but it will be a huge problem and an ecological disaster," Kuleba told RFE/RL.
"We are also anticipating that water level in the Kakhovka basin will drop dramatically and this will lead to a complete change of the ecological environment of the Kherson region. It is necessary to get ready for that as well," he said.
SLIDER IMAGE: The Nova Kakhovka Dam Before And After The Explosion
The Nova Kakhovka dam -- which is 30 meters tall and 3.2 kilometers long -- is part a vital route for transport and irrigation, as well as supplying water to Ukraine's Crimean Peninsula and the Zaporizhzhya nuclear plant, which are both under Russian control.
"Russian terrorists," Zelenskiy wrote on Twitter, where he posted a video of the broken dam showing the water rapidly flowing through the huge breach.
"The destruction of the [Nova] Kakhovka hydroelectric power plant dam only confirms for the whole world that they must be expelled from every corner of Ukrainian land. Not a single meter should be left to them, because they use every meter for terror.... The terrorists will not be able to stop Ukraine with water, missiles, or anything else," Zelenskiy wrote, adding that all services were working.
Speaking later in a video address to the Bucharest Nine summit being held in Bratislava, Zelenskiy said the Russian claims were impossible given the size of the structure, which Moscow had controlled for more than a year.
"It is physically impossible to blow it up somehow from the outside -- with shelling. It was mined. It was mined by the Russian occupiers and blown up by them," he said.
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Water Rising To 'Critical' Levels, Says Ukrainian Official After Dam Break
Natalya Humenyuk, the spokeswoman for Ukraine's southern military command, said Russia blew up the dam to keep Ukrainian troops from being able to cross the Dnieper as it prepares to go on the counteroffensive to push Russian troops out of the region.
"They were aware that the movement of the [Ukrainian] defense forces would take place and in this way tried to influence the defense forces so that the crossing of the Dnieper, which they feared, would not happen," she told an online briefing, calling it a "hysterical reaction."
United Nations Secretary-General Antonio Guterres labeled the destruction of the dam a "monumental humanitarian, economic and ecological catastrophe" in a statement but stopped short of blaming Russia directly. Ahead of an emergency UN Security Council meeting, Guterres called it “another devastating consequence of the Russian invasion of Ukraine.”
Ihor Syrota, the head of Ukrhydroenergo, said in an interview on state television that the hydro power station that formed part of the dam was "completely destroyed."
Syrota told RFE/RL that the rising water is expected to peak early on June 7 and will begin to recede on the third or fourth day.
Russia denied it carried out the attack, with the Kremlin instead calling it "deliberate sabotage" by Kyiv.
The Moscow-installed mayor of Nova Kakhovka, Vladimir Leontyev said Ukrainian strikes on the dam destroyed its valves, and “water from the Kakhovka reservoir began to uncontrollably flow downstream.”
Russian Defense Minister Sergei Shoigu charged that Ukraine destroyed the dam to prevent Russian attacks in the Kherson region after what he alleged was a failed Ukrainian counteroffensive.
The International Atomic Energy Agency (IAEA) said the Zaporizhzhya nuclear plant has enough water to cool its reactors for "several months" from a pond located above the reservoir.
"There are a number of alternative sources of water. A main one is the large cooling pond next to the site that by design is kept above the height of the reservoir," IAEA chief Rafael Grossi said in a statement.
"It is therefore vital that this cooling pond remains intact. Nothing must be done to potentially undermine its integrity. I call on all sides to ensure nothing is done to undermine that," Grossi said.
Before it was breached the dam's reservoir provided water used for the cooling of the plant’s six reactors as well as spent fuel and emergency diesel generators.
International condemnation of the attack was swift, with NATO chief Jens Stoltenberg calling it "an outrageous act," while European Council President Charles Michel expressed “shock” saying Russia should be held accountable for the "war crime" of destroying civilian infrastructure.
Mass Evacuations Follow Breach Of Ukrainian Dam
British Foreign Secretary James Cleverly also put the blame squarely on Moscow for the destruction of the dam, saying that while it was "too early" to make any kind of meaningful assessment of the details, "it's worth remembering that the only reason this is an issue at all is because of Russia's unprovoked full-scale invasion of Ukraine."
German Chancellor Olaf Scholz pointed the finger for the destruction squarely at Moscow.
"This is of course, by all accounts, an aggression by the Russian side to stop the Ukrainian offensive to defend its own country," Scholz told broadcaster RTL.
White House National Security Council spokesman John Kirby also reacted to the destruction of the dam, saying U.S. President Joe Biden had been briefed.
Kirby told reporters that the U.S. “cannot say conclusively what happened” and declined to assess the impact on Ukraine’s counteroffensive.
He said the U.S. government expects "significant damage" to the people of Ukraine and the region.
"We know there are casualties, including likely many deaths, though these are early reports and we can't quantify them right now," he said, warning that the destruction of the power plant could have a devastating impact on Ukraine's energy security.