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 worldwide nuclear power," President Volodymyr Zelenskiy said in his nightly video address.
He decried the Russian presence as "radiation blackmail".
His comments followed a meeting with Rafael Grossi, the director-general of the International Atomic Energy Agency (IAEA). The two met on Monday at the Dnipro hydroelectric power station, northeast of the Zaporizhzhia plant.
Initiatives on restoring safety and security are "doomed to failure" without an immediate 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 he is due to visit it again this week.Â
Zaporizhzhia is one of four regions Russia claimed to annex in September after referendums slammed 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.
Analysts expect a Ukrainian counterattack to get under way in April-May as the weather improves and more military aid arrives, including battle tanks Leopard and Challenger.
The 18 Leopard 2 tanks, workhorse of militaries across Europe, pledged by Germany have reached Ukraine, the German defence ministry said on Monday.
"I'm sure that they can make a decisive contribution on the front," German Defence Minister Boris Pistorius said on Twitter.
Front lines in Ukraine have barely moved for more than four months despite a Russian winter offensive. Ukraine's military aims to wear down Russian forces before mounting its own attack.
Russia's Wagner mercenary force, which fights alongside Russian forces in eastern Ukraine and is thought to have sustained heavy losses, is seeking to replenish its ranks before any Ukrainian counteroffensive.
A giant recruitment advertisement for the group has appeared on the facade of an office building in northeast Moscow.
It shows Wagner's logo and slogans such as "Join the winning team!" and "Together we will win".
On the battlefield, Russian forces appear to be focusing on Avdiivka, 90 kilometres south of the battered mining town of Bakhmut.
Ukraine shut Avdiivka to civilians on Monday, with an official describing the town as a "post-apocalyptic" wasteland.
The Ukrainian military has warned that Avdiivka could become a "second Bakhmut", which has been reduced to rubble in months of fighting that both sides have called a "meat grinder". Russian forces say they are fighting street by street.
Since Putin's invasion to "demilitarise" Ukraine got bogged down in the autumn, he and other Russian officials have played up the prospect the war could escalate to involve nuclear weapons.
On Saturday, he said he had struck a deal to station tactical nuclear weapons in Belarus.
Ukraine and its Western allies have denounced the plan.
Ukraine called for a meeting of the UN Security Council, and Lithuania said it would call for new sanctions against Moscow and Minsk. EU policy chief Josep Borrell urged Belarus not to host the weapons and threatened more sanctions.
