Foreign ministers from the G7 group of nations say Russia must immediately hand back control of the Zaporizhzhia nuclear power plant to Ukraine.
They accused Moscow’s forces of putting the entire region in danger.
The facility and its surrounding area saw shelling last week, which Russia and Ukraine blamed on each other.
Ukraine says Russia has turned the site into a military base, launching attacks from there knowing that Ukrainian forces are unlikely to retaliate.
The complex, Europe’s largest, has been under Russian occupation since early March, although Ukrainian technicians still operate it.
Petro Kotin, the head of Enerhoatom, Ukraine’s nuclear power operator, told the BBC earlier this week that about 500 Russian soldiers were at the site, using it as a nuclear shield.
Mr Kotin said the threat was grave, but that the plant remained safe.
In other developments:
- Ukraine’s Air Force command says about a dozen Russian warplanes may have been destroyed in explosions at an airfield in Russian-occupied Crimea on Tuesday
- Ukraine has denied any responsibility for the blasts and Russia’s defence ministry said ammunition detonated at the base
- The Ukrainian military reports a bridge in the occupied part of Kherson Region has been rendered unusable after being struck by artillery earlier in the week. Ukraine has mounted a counteroffensive in the area
- Russian investigators have launched a criminal inquiry against journalist Marina Ovsyannikova, who denounced Russia’s invasion on live TV
Ministers from the G7, an organisation of some of the world’s wealthiest nations, said they were profoundly concerned over the serious threat to safety at the nuclear plant.
Their warning echoed statements from the United Nations’ nuclear watchdog, the International Atomic Energy Agency (IAEA), which called for an end to “all military activities that endanger nuclear security”.
However, the chances that Russia will take heed appear extremely remote at best, say analysts.
The G7 also said Russia’s actions undermined the IAEA’s ability to monitor the safety of nuclear activities in Ukraine.
For its part, Russia has accused Ukraine of creating “artificial obstacles and difficulties” to a potential IAEA mission to the nuclear power plant.
Russia has requested an urgent meeting of the UN Security Council to discuss the situation at the power plant. The meeting will be held on Thursday in New York.
Meanwhile, Ukrainian officials say Russian shelling in central Ukraine overnight killed at least 16 people.
Thirteen of the victims were in the Dnipropetrovsk region, two died in the Donetsk region, and a woman was killed in the Zaporizhzhia region.