Ukraine's Foreign Ministry on Tuesday called for an urgent meeting of the UN Security Council to discuss a “Russian terrorist attack”, as the warring countries blamed each other for the destruction of the Kakhovka dam.
Thousands of people were left at critical risk from flooding as a result of the destruction of the site overnight.
Water flooded several areas downstream in the hours after an explosion at the site, which is on the Dnipro river that separates Russian and Ukrainian forces in southern Ukraine.
Both Russian and Ukrainian authorities brought in trains and buses for residents.
Neither side reported any deaths or injuries.
Videos posted online showed floodwater inundating a long road and a beaver scurrying for high ground from rising waters.
Ukraine’s presidential office said about 150 tonnes of oil escaped from the dam machinery and that another 300 tonnes could still leak out.
Mykhailo Podolyak, a senior adviser to President Volodymyr Zelenskyy, said on Tuesday morning that “a global ecological disaster is playing out now, online, and thousands of animals and ecosystems will be destroyed in the next few hours.”
Blame and counter claim
Ukraine’s state hydro power generating company said the hydroelectric dam was “completely destroyed”, accusing of Russia blowing up the station from inside the engine room.
“The station cannot be restored,” it added.
Russian investigators said they have started a criminal investigation into the dam's destruction, while Ukraine’s prosecutor general’s office said it is investigating the blast as a “war crime and environmental crime”.
Speaking on Tuesday morning, Yuriy Sak, an adviser to Ukraine's Defence Ministry, said interceptions of calls between Russian forces indicated Moscow was to blame for the dam's destruction. He called it a “desperate attempt” to thwart Ukraine's counter-offensive.
“Russian soldiers are telling each other this is their fault. They are actually calling to blow up more dams on the Dnipro River,” he told BBC Radio 4.
“We understand that what is happening is Russia’s desperate attempt to somehow influence our plans, our offensive.”
Russia, in turn, blamed Ukraine, with news agencies reporting the dam had been destroyed by shelling, while the mayor of Russia-controlled Nova Kahhovka city was quoted as saying it was a result of an act of “terrorism”.
UK Foreign Secretary James Cleverly, who visited Ukraine on Tuesday, said that the damage was a “catastrophe” and an “abhorrent act”.
“Intentionally attacking exclusively civilian infrastructure is a war crime,” he said.
“The UK stands ready to support Ukraine and those affected by this catastrophe.”
British Prime Minister Rishi Sunak said the destruction of the Kakhovka dam in Ukraine would mark a “new low” in the conflict if Russian forces were found to be responsible.
He said the immediate priority was the humanitarian response to the catastrophe.
Mr Sunak, speaking to reporters as he travelled to Washington for talks with US President Joe Biden, said if it was an intentional act to blow up the dam it would be “the largest attack on civilian infrastructure” since the start of Russia’s war.
He said that attacks on civilian infrastructure were “appalling and wrong”.
'All sorts of reasons'
It was not immediately clear how either side would benefit from the damage to the dam, since both Russian-controlled and Ukrainian-held territory is at risk.
The damage could hinder Ukraine’s counter-offensive in the south and distract its government, while Russia depends on the dam to supply water to Crimea.
The reservoir feeds the Soviet-era North Crimean Canal – a channel which has traditionally supplied 85 per cent of Crimea's water. Most of that water is used for agriculture, some for industry, and about one fifth for drinking water and other public needs.
Patricia Lewis, director of the International Security Programme at the UK-based Chatham House think tank, said apportioning blame is difficult but “there are all sorts of reasons why Russia would do this.”
“There were reports [last autumn] of Russians having mined the reservoir. The question we should pose is why the Ukrainians would do this to themselves, given this is Ukrainian territory,” she said.
Experts have previously said the dam was suffering from disrepair. David Helms, a retired American scientist who has monitored the reservoir since the start of the war, said that it was not clear if the damage was deliberate or simply the results of neglect by Russian forces occupying the plant.
But Mr Helms reserved judgment, also noting that Russia has a history of attacking dams.
'Fine job, soldiers in the Bakhmut sector'
It comes shortly after what appeared to be the start of Ukraine's long-awaited counter-offensive to reclaim territory seized by Russia.
In his nightly address on Monday, Mr Zelenskyy welcomed “the news we have been waiting for” from troops fighting in and around the shattered eastern city of Bakhmut, but gave no further details.
“I am grateful to each soldier, to all our defenders, men and women, who have given us today the news we have been waiting for. Fine job, soldiers in the Bakhmut sector,” Mr Zelenskyy said.
Footage from what appeared to be a monitoring camera overlooking the dam that was circulating on social media purported to show an explosion and breakage.
The area’s Moscow-installed authorities said it was partially destroyed by “multiple strikes” damaging the gate valves, which resulted in an “uncontrollable” flow of water.
Mr Zelenskyy convened an urgent National Security Council meeting, calling the incident “another war crime committed by Russian terrorists”.
Ukraine's interior ministry advised residents of 10 villages on the river’s right bank to evacuate, along with people in some downstream areas of Kherson.
Mr Zelenskyy later said “all services are working” at the dam and the explosion “only confirms for the whole world that [Russia] must be expelled from every corner of Ukrainian land”.
“It’s only Ukraine's victory that will return security. And this victory will come. The terrorists will not be able to stop Ukraine with water, missiles or anything else,” he said on Twitter.
The dam supplies water to the Zaporizhzhia nuclear plant and Crimea, which was annexed by Russia in 2014.
The Ukraine War Environmental Consequences Working Group said a total collapse of the dam would wash away much of the left bank, and a severe drop in the reservoir has the potential to deprive the nuclear plant of crucial cooling, as well as dry up the water supply in northern Crimea.
The nuclear plant is controlled by Russian forces. Ukraine previously said it expected a Russian attack on the dam to try to flood some areas.
The head of Ukraine's state nuclear energy company said on Tuesday that the situation at the plant iwas s “not critical”.
Energoatom chief Petro Kotin said the fall in the levels of the Kakhovka reservoir would not affect the level of water in cooling ponds at the facility's spent nuclear fuel storage pools.
The International Atomic Energy Association wrote on Twitter that there was “no immediate nuclear safety risk at [the] plant.”
The volume of water in the Kakhovka reservoir is about equal to that of the Great Salt Lake in the US state of Utah.
Officials installed by Moscow said Crimea's water supply would be affected.
Ukraine controls five of the six dams along the Dnipro river, which runs from its northern border with Belarus down to the Black Sea and is crucial for the entire country’s drinking water and power supply.
The Kakhovka dam is furthest downstream in the Kherson region.