KYIV: Ukraine on Tuesday accused Russian forces of blowing up a major dam and hydroelectric power station in a part of southern Ukraine that Moscow controls, sending water gushing from the breached facility and threatening what officials called an "ecological disaster" due to possible massive flooding.
Officials from both sides of the war ordered hundreds of thousands of residents downriver to evacuate.
Russian officials countered that the Kakhovka dam, on the Dnipro River, was damaged by Ukrainian military strikes in the contested area.
The fallout could have broad consequences: Flooding homes, streets and businesses downstream; depleting water levels upstream that help cool Europe's largest nuclear power plant; and draining supplies of drinking water to the south in Crimea, which Russia illegally annexed.
The dam break added a complex new element to Russia's ongoing war in Ukraine, now in its 16th month.
Ukrainian forces were widely seen to be moving forward with a long-anticipated counteroffensive in patches along more than 1,000 kilometres of the frontline in the east and south of Ukraine.
Ukraine's nuclear operator Energoatom said in a Telegram statement that the blowing up of the dam "could have negative consequences" for the Zaporizhzhia Nuclear Power Plant, which is Europe's biggest, but wrote that for now, the situation is "controllable".
The UN's International Atomic Energy Agency wrote on Twitter that its experts were closely monitoring the situation at the plant, and there was "no immediate nuclear safety risk" at the facility.
Ukrainian authorities have previously warned that the dam's failure could unleash 18 million cubic metres (4.8 billion gallons) of water and flood Kherson and dozens of other areas where hundreds of thousands of people live.
The World Data Center for Geoinformatics and Sustainable Development, a Ukrainian nongovernmental organisation, estimated that nearly 100 villages and towns would be flooded.
It also reckoned that the water level would start dropping only after five to seven days.
A total collapse in 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, according to the Ukraine War Environmental Consequences Working Group, an organisation of environmental activists and experts documenting the war's environmental effects.
Mykhailo Podolyak, a senior advisor to President Volodymyr Zelenskyy, said that "a global ecological disaster is playing out now, online, and thousands of animals and ecosystems will be destroyed in the next few hours".
Videos posted online began testifying to the spillover.
This video shows the Kakhovka Hydroelectric Power Plant. Around 16,000 people's homes in Kherson Oblast are located in "critical risk" zones for flooding after Russian forces blew up the plant.