President Volodymyr Zelenskiy said on Thursday Ukrainian spies had received information showing Russia was considering carrying out a "terrorist" attack at the Zaporizhzhia nuclear plant involving a release of radiation.
The Kremlin dismissed the allegation as "another lie" and said a team of UN nuclear inspectors had visited the plant and rated everything highly.
In a video statement on the Telegram messenger, Zelenskiy said Kyiv was sharing the information about the Russian-occupied facility in southern Ukraine with all its international partners from Europe and the United States to China and India.
"Intelligence has received information that Russia is considering the scenario of a terrorist act at the Zaporizhzhia nuclear plant - a terrorist act with the release of radiation," he said. "They have prepared everything for this."
Zelenskiy did not say what evidence the intelligence agencies based their assertion on.
The six-reactor complex, Europe's biggest nuclear plant, has been under occupation since shortly after Moscow's forces invaded Ukraine in February last year.
The two sides have accused each other of shelling the vast complex, and international efforts to establish a demilitarized zone around it have failed so far.
"Unfortunately, I have had to remind (people) more than once that radiation knows no state borders. And who it will hit is determined only by the direction of the wind..." Zelenskiy said.
Ukraine, then part of the Soviet Union, suffered the world's worst nuclear accident in 1986, when clouds of radioactive material spread across much of Europe after an explosion and fire at the Chornobyl nuclear power plant.
Zelenskiy made his statement two days after Ukraine's military intelligence chief accused Russia of "mining" the cooling pond that is used to keep the reactors cool at the Zaporizhzhia plant.
Russian forces have occupied swathes of Ukraine's south and east, and Moscow has unilaterally declared them a part of Russia. Moscow plans to conduct elections on the occupied territory there this September.
