A United Nations official issued a stern warning after Ukraine’s main nuclear plant was shelled, saying, “You are playing with fire.

An attack on Ukraine’s Zaporizhzhia nuclear power plant, which is controlled by Russia, drew strong criticism from the UN nuclear watchdog on Sunday, as such assaults risk a cataclysmic disaster.

The International Atomic Energy Agency (IAEA) said that more than a dozen explosions jolted Europe’s largest nuclear power plant on Saturday and Sunday evenings.

Both Moscow and Kyiv blamed the other for shelling the facility, as they have frequently done in recent months after earlier blasts.

There has been repeated shelling of a plant in southern Ukraine, raising concern about the possibility of a severe accident just 500 kilometers (300 miles) from the site of the Chornobyl nuclear disaster, the world’s most serious nuclear accident.

Before Russia’s invasion, the Zaporizhzhia nuclear power plant provided about a fifth of Ukraine’s electricity. Six Soviet-designed VVER-1000 V-320 water-cooled and water-moderated reactors containing Uranium 235 have been forced to operate on backup generators several times.

The Chornobyl nuclear accident in Ukraine in 1986, which killed thousands of people, has led experts to express concern that repeated shelling of the plant during the war could lead to a grave disaster.

The near miss at Europe’s largest atomic power plant during weekend fighting, in which shells rained down on it and damaged a radioactive waste storage building, was described by the UN nuclear watchdog as a “close call.”