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.”

The Zaporizhzhia nuclear power plant, invaded by Russia on Feb. 24, is unsure whether there was an explosion on the Ukrainian side.

According to Rafael Grossi, director general of the International Atomic Energy Agency (IAEA), whoever attacked the plant was taking huge risks and gambling with many people’s lives.

The IAEA said radiation levels remained normal, and there were no reports of casualties, although “the shelling came dangerously close to them.” Thankfully, nuclear safety and security systems were not directly impacted.

Battles have been raging to the east of Zaporizhzhia, near the same Dnipro river where Kherson was recently recaptured, following troop movements from around the city.

In response to military setbacks, Russia has fired a barrage of missiles, many of which targeted power facilities and left the country without electricity as winter approached and temperatures dropped.

An IAEA team on the ground said that damaged infrastructure, including a radioactive waste and storage facility, cooling pond systems, a cable to one of the reactors, and a bridge to another reactor and auxiliary structures, were all damaged.

On Tuesday, Grossi said the team would conduct an assessment, but Russian nuclear power operator Rosenergoatom noted that the team would be restricted in its inspection.

An advisor to Rosenergoatom’s CEO, Renat Karchaa, told Tass that if the facility being inspected had no connection to nuclear safety, access would be denied.

Before Russia’s invasion, Zaporizhzhia provided about a fifth of Ukraine’s electricity and has been forced to operate on backup generators several times. The six Soviet-designed VVER-1000 V-320 water-cooled and water-moderated Uranium 235 reactors are water-moderated and water-cooled.

There is a danger that nuclear fuel might overheat if the cooling systems’ power supply is cut off. Shelling has repeatedly cut power lines.

According to Russia’s defense ministry, Ukraine damaged the power lines that supplied the facility. Energoatom, Ukraine’s nuclear energy company, said that Russia’s military had shelled the site in the act of nuclear blackmail that endangered the world at large.

President Volodymyr Zelensky said in a video address on Sunday evening that eastern Ukraine was the scene of the heaviest Russian artillery assaults on Ukrainian frontline positions.

Russia has redeployed troops from the southern city of Kherson to the Donetsk and Luhansk regions in the east, and in Donbas.

Despite the bad weather today, the Donetsk region continues to see the most fierce battles, Zelensky said. Unfortunately, the amount of Russian shelling remains extremely high.

“In the Luhansk region, we are slowly moving forward while fighting. As of now, there have been almost 400 artillery attacks in the east since the start of the day,” Zelensky said.

According to an early Monday update from Ukraine’s military, Russian forces have shelled the Luhansk region in the east and Kharkiv in the northeast, while Ukrainian forces have repelled Russian attacks in Donetsk.

Battlefield reports could not be immediately verified by Reuters.

Zelensky said troops were “consistently and very calculatedly destroying the potential of the occupiers.”

As of writing, there is no electricity, running water, or heating in Kherson city.

According to military analyst Oleh Zhdanov, Russian offensives were taking place on the Bakhmut and Avdiivka frontlines in Donetsk, among other sites.

Zhdanov added the enemy has so far been unable to break through our defenses. 

“We fight back – they suffer significant losses,” he said.

UN’s Official Warning