Kyiv, NATO and the European Union have blamed Moscow for the attack on the dam, which is in an area currently held by the Russian forces of occupation.

Russia has blamed Ukraine.

“Italy powerfully condemns the bombing of the Kakhovka dam in the Kherson region, which is endangering thousands of people and is provoking an ecological disaster, further aggravating the humanitarian emergency,” the Italian foreign ministry quoted Tajani as saying.

“I am following developments with utmost attention and concern, including in relation to the possible consequences for the security of the Zaporizhzhia nuclear plant.

“We are at the side of our Ukrainian friends and of all the civilians who are suffering the consequences of this additional, brutal attack”.

A torrent of water burst through the dam on the Dnipro River that separates Russian and Ukrainian forces in southern Ukraine, flooding a swathe of the war zone, forcing villagers to flee and prompting finger-pointing from both sides.

Ukraine said Russia had committed a deliberate war crime in blowing up the Soviet-era Nova Kakhovka dam, which powered a hydroelectric station.

The Kremlin blamed Ukraine, saying it was trying to distract from the launch of a major counteroffensive Moscow says is faltering.

Some Russian-installed officials said the dam had collapsed on its own, while Washington said it was uncertain who was responsible.

But Deputy US Ambassador to the United Nations Robert Wood told reporters it would not make sense for Ukraine to destroy the dam.

Neither side offered immediate public evidence of who was to blame.

The Geneva Conventions ban targeting dams in war because of the danger to civilians.

Ukrainian President Volodymyr Zelenskiy said in a video address that his prosecutors had already approached the International Criminal Court about the dam incident.

Earlier, he claimed on Telegram that Russian forces blew up the power plant from inside.

Buses, trains and private vehicles were marshalled to carry people to safety while some people waded in knee-deep water, carrying pets and luggage.

Ukrainian officials reported more than a thousand people rescued from Kherson city along with residents evacuated from flooded towns and villages.

A Russian-installed official said some 22,000 people in the Kherson region were at risk, RIA news agency said.

It was not immediately clear if anyone died but US spokesman John Kirby said it had probably caused “many deaths”.

Flooding would peak on Wednesday then levels would start to fall within three to four days, Ihor Syrota, head of Ukraine’s hydroelectric power authority, told the US-funded radio station Donbas Realii.

The Kazkova Dibrova Zoo on the Russian-held riverbank was completely flooded and all 300 animals were dead, a representative said via the zoo’s Facebook account.

The dam supplies water to a wide area of southern Ukrainian farmland, including the Russian-occupied Crimean peninsula, as well as cooling the Russian-held Zaporizhzhia nuclear plant.

The dam’s destruction threatens a new humanitarian disaster in the centre of the war zone and transformed the front lines just as Ukraine prepares a long-awaited counteroffensive to drive Russian troops from its territory.

Russia has controlled the dam since early in its 15-month-old invasion, although Ukrainian forces recaptured the Dnipro’s northern bank last year.

Both sides had long accused the other of plotting to destroy the dam.

UN Secretary-General Antonio Guterres said the UN had no independent information on how the dam was breached, describing it as “another devastating consequence” of Russia’s invasion.

The UN Security Council was meeting to discuss the dam at the request of both Russia and Ukraine.

ANSA & AAP