Ukrainian President Volodymyr Zelensky warned on Saturday that a “serious threat" remained at the Russian-occupied Zaporizhzhia nuclear power plant.
He said Russia was “technically ready" to provoke a localized explosion at the facility and cited Ukrainian intelligence as the source of his information.
“There is a serious threat because Russia is technically ready to provoke a local explosion at the station, which could lead to a [radiation] release," he told a joint news conference in Kyiv with visiting Spanish Prime Minister Pedro Sanchez.
The Ukrainian leader gave no further details, but Kyiv has previously claimed Russian troops have mined the plant.
Mr Zelenskiy called for greater international attention to the situation at the facility in southeastern Ukraine, which is Europe’s largest nuclear plant.
He also urged sanctions on Russia’s state nuclear company Rosatom.
The Zaporizhzhia nuclear plant, located near the city of Enerhodar in southern Ukraine, has been occupied by Russia since early March last year, shortly after Moscow’s invasion.
Russia has previously denied Kyiv’s accusations that Russia was preparing an explosion at the plant. Kyiv and Moscow have accused each other of shelling the facility.
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 Chernobyl nuclear power plant.
The warning came as satellite images separately appeared to show a camp being built in Belarus to house Wagner fighters.
Chief of the Russian mercenary force Yevgeny Prigozhin and his fighters escaped prosecution and were offered refuge in Belarus last week after Minsk helped broker a deal to end what appeared to be an armed insurrection in Russia.
The abortive revolt saw Wagner troops capture a military headquarters in southern Russia and march hundreds of miles towards Moscow.
The images suggested that dozens of tents have been erected within the past two weeks at a former military base outside Osipovichi, a town 142 miles north of the Ukrainian border.
Belarus’s authoritarian leader Alexander Lukashenko said his country, a close ally of Moscow, could use Wagner’s experience and expertise, and announced that he had offered the fighters an “abandoned military unit" to set up camp.