Ukraine's president said Russian troops were holding the Zaporizhzhia nuclear plant "hostage" and its safety could not be guaranteed until they left it, while his forces shut the frontline town of Avdiivka as they planned their next move.
Russian troops have occupied the nuclear power plant, Europe's largest, since the early weeks of the invasion of Ukraine and have shown no inclination to relinquish control.
"Holding a nuclear power station hostage for more than a year - this is surely the worst thing that has ever happened in the history of European or world-wide nuclear power," President Volodymyr Zelenskiy said in his nightly video address.
Reuters reporting him describing the Russian presence as "radiation blackmail".
His comments followed a meeting with Rafael Grossi, the director general of the International Atomic Energy Agency (IAEA), at the Dnipro hydroelectric power station - northeast of the Zaporizhzhia plant.
Initiatives on restoring safety and security are "doomed to failure" without a withdrawal of Russian troops from the plant, Zelenskiy said in comments posted on the presidential website.
Russia and Ukraine routinely accuse each other of shelling the Zaporizhzhia plant. Fighting around it and worries of a water shortage and that cooling systems could lose power have raised fears of a nuclear disaster.
A team of IAEA has since September been stationed at the plant, which Kyiv has accused Moscow of using as a shield for troops and military hardware.
Grossi has repeatedly called for a safety zone around it and is due to visit it again this week. He has tried to negotiate with both sides but said in January that brokering a deal was getting harder.
Zaporizhzhia is one of four regions Russia claimed to annex in September after referendums criticised globally as shams. Russia views the plant as its territory, which Ukraine denies.
Zelenskiy visited the southeastern Zaporizhzhia region on Monday, the latest stage of a tour of frontline regions since a top general said Ukraine's counterattack could come soon.