Turkey’s President Recep Tayyip Erdogan on Wednesday proposed, in a call with Ukrainian President Volodymyr Zelensky, creating an international commission to probe the destruction of the dam, his office reported.

“President Erdogan said that a commission could be established with the participation of experts from the warring parties, the United Nations and the international community, including Turkey, for a detailed investigation into the explosion at Kakhovka dam,” his office said after the call.

The UN Security Council held an emergency meeting on Tuesday following requests from Russia and Ukraine.

“Today’s news means the plight of the people in Ukraine is set to get even worse,” the UN’s top humanitarian official Martin Griffiths told the meeting.

The UN warned that hundreds of thousands could be affected on both sides of the front line.

People in Kherson, the largest population centre nearby, headed for higher ground as water poured into the Dnipro River.

Ukrainian authorities said 17,000 people were being evacuated and a total of 24 villages had been flooded.

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“Over 40,000 people are in danger of being flooded,” Prosecutor General Andriy Kostin said, adding that 25,000 more people needed to be evacuated on the Russian-occupied side of the Dnipro.

“The evacuation will continue tomorrow and in the coming days – by bus and train,” presidential adviser Oleksiy Kuleba said late Tuesday.

Zelensky accused Russia of detonating an “environmental bomb of mass destruction”, saying authorities expected up to 80 settlements to be flooded and urging the world to “react”.

“This crime carries enormous threats and will have dire consequences for people’s lives and the environment,” Zelensky said.

But the explosion would “not affect Ukraine’s ability to de-occupy its own territories”, he added.

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

Last October, Zelensky accused Russia of planting mines at the dam, warning that its destruction would spur a new wave of refugees into Europe.

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Kyiv said 150 tonnes of engine oil had spilled into the river, and the agricultural ministry said about 10 thousand hectares of farmland on the right bank of the river would be flooded and “several times more” on the left bank.

Western powers also blamed Russia for the damage, with EU chief Charles Michel calling it a “war crime”, while Nato chief Jens Stoltenberg said the dam breach was “outrageous”.

The United States “cannot say conclusively what happened at this point,” National Security Council spokesman John Kirby told reporters.

British Prime Minister Rishi Sunak said that the country’s military and intelligence agencies were probing whether Russia blew up the dam, but that it was “too soon” to say definitively.

UN Secretary General Antonio Guterres called the attack “another devastating consequence of the Russian invasion of Ukraine”.

“Today’s tragedy is yet another example of the horrific price of war on people,” he said.

China’s UN ambassador Zhang Jun said: “We express our grave concern over the destruction of the dam at the Kakhovka hydroelectric power plant. We are deeply concerned about the resulting humanitarian, economic, and ecological consequences. We call on all parties to the conflict to abide by international humanitarian law and do their utmost to protect civilians and civilian infrastructure”.

Russia said the dam was partially destroyed by “multiple strikes” from Ukrainian forces and urged the world to condemn Kyiv’s “criminal acts”.

Kremlin spokesman Dmitry Peskov said the destruction was the result of “deliberate sabotage by the Ukrainian side”.

The Soviet-era dam, built in the 1950s, sits on the Dnipro River, which provides cooling water for the Russian-occupied Zaporizhzhia nuclear power plant some 150km (90 miles) away.

Moscow and Kyiv offered conflicting assessments of the safety of the facility.

The Russian-installed director of the plant, Yuri Chernichuk, said water levels in the cooling pond had not changed and “at the moment, there is no security threat to the Zaporizhzhia nuclear power plant”.

Ukraine, then part of the Soviet Union, suffered the devastating Chernobyl nuclear disaster in 1986, and its authorities sounded the alarm over the Kakhovka breach.

“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.

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The Ukrainian nuclear operator, Energoatom, said the water level of the Kakhovka reservoir was “rapidly decreasing, which is an additional threat” to the Zaporizhzhia plant.

The UN humanitarian agency said it was concerned about “the severe humanitarian impact on hundreds of thousands of people on both sides of the front line”.

“Flooding and fast-moving water can move mines and explosive ordnance to new areas which previously had been assessed as safe, thus putting more people in danger.”

Ukrainian Foreign Minister Dmytro Kuleba wrote on Twitter that the EU had pledged “necessary assistance and humanitarian aid to mitigate the consequences of this Russia-made disaster”.

Additional reporting by Associated Press and Reuters