An attack on a major Russian-held dam in southern Ukraine Tuesday unleashed a torrent of water that flooded a small city, two dozen villages and sparked the evacuation of 17,000 people.
Moscow and Kyiv traded blame for ripping a gaping hole in the Kakhovka dam in what Kyiv said was an attempt by Russia to hamper Ukraine's long-awaited offensive.
People in the city of Kherson, the largest population centre nearby, headed for higher ground as water, which had been held back by the dam and a hydroelectric plant, rose in the Dnipro River.
"There is shooting, now there is flooding," said Lyudmyla, who had loaded a washing machine onto a cart that was attached to an old Soviet car.
"Everything is going to die here," added Sergiy as water from the dam poured downstream into Kherson.
Ukrainian authorities said 17,000 people were being evacuated and a total of 24 villages had been flooded.
"Over 40,000 people are in danger of being flooded," Prosecutor General Andriy Kostin said, adding that 25,000 more people should be evacuated on the Russian-occupied side of the Dnipro River.
Vladimir Leontyev, the Moscow-installed mayor of Nova Kakhovka where the dam is located, said the city was underwater and 900 people had been evacuated.
He said 53 evacuation buses were being sent by the authorities to take people from Nova Kakhovka and two other settlements nearby to safety.
"We are organising temporary accommodation centres with hot meals," he said.
The Kakhovka dam and its power plant were seized by Russia in the first hours of the war.
'War crime'
Ukrainian President Volodymyr Zelensky accused Russia of blowing up the dam, urging the world to "react."
He said Russia had carried out "an internal explosion of the structures" of the plant at 2:50 am local time (2350 GMT).
"This crime carries enormous threats and will have dire consequences for people's lives and the environment," Zelensky told a Vatican peace envoy, Italian cardinal Matteo Zuppi, in Kyiv, the presidency said.
Kyiv also called for a meeting of the UN Security Council and warned of a potential "ecocide" after 150 tonnes of engine oil spilled into the river as a result of the attack.
Western powers also blamed Russia for the damage to the Kakhovka dam, with EU chief Charles Michel calling it a "war crime."
NATO chief Jens Stoltenberg said the dam breach was "outrageous" and "puts thousands of civilians at risk and causes severe environmental damage."
Russia however said the dam was partially destroyed by "multiple strikes" coming from Ukrainian forces.
Kremlin spokesman Dmitry Peskov said the destruction was the result of "deliberate sabotage by the Ukrainian side."
The Soviet-era dam sits on the Dnipro River, which provides cooling water for the Russian-occupied Zaporizhzhia nuclear power plant.
The flooding heightened existing fears for the safety of the Zaporizhzhia plant, the largest in Europe.
The plant is some 150 kilometres (about 90 miles) away from the damaged dam.
Moscow and Kyiv offered conflicting versions on the safety of the facility.
The Russian-installed director of the plant, Yuri Chernichuk, echoed the UN agency and said that "at the moment, there is no security threat to the Zaporizhzhia nuclear power plant."
"The water level in the cooling pond has not changed," he said, adding that the situation was under control.
Chernichuk said the water cooling system was not in direct contact with the outside environment and could be refilled from several alternative sources.
'Russia loses 71 soldiers'
But Ukraine, which in 1986 suffered the devastating Chernobyl nuclear disaster, sounded the alarm.
"The world once again finds itself on the brink of a nuclear disaster, because the Zaporizhzhia nuclear power plant lost its source of cooling. And this danger is now growing rapidly," Zelensky's aide Mykhaylo Podolyak said.
The Ukrainian nuclear operator, Energoatom, said the water level of the Kakhovka reservoir was "rapidly decreasing, which is an additional threat to the temporarily occupied Zaporizhzhia nuclear power plant."
News of the damage came after Russia claimed Ukraine had begun a long-expected counter-offensive to claw back lost territory after Moscow invaded in February, 2022.
On Tuesday, Defence Minister Sergei Shoigu announced that Moscow had halted Kyiv's offensive but lost 71 soldiers over the past three days, an extremely rare admission of Russia's losses.
On Monday, Zelensky praised his troops for advances claimed near the devastated city of Bakhmut.
Kyiv already accused Moscow of mining the dam as combat raged nearby in October, during the last major offensive by Ukrainian forces seeking to regain lost territory. Russia denies the claim.
Built in the 1950s, the Kakhovka dam has strategic value as it pumps water into the North Crimean Canal, which starts in southern Ukraine and crosses the entire Crimean peninsula.
This means that any problem with the dam could cause water supply problems for Crimea, which has been under Russian control since 2014.