KYIV, UKRAINE -- An explosion caused by an alleged drone attack at Europe鈥檚 largest nuclear plant in Ukraine on Tuesday posed no direct threat to its safety but underscored the 鈥渆xtremely serious situation鈥 at the facility that repeatedly has been caught in the war's crossfire, the UN鈥檚 atomic watchdog agency said.

The International Atomic Energy Agency said its team was aware of an at a training centre next to the plant. It said it was 鈥渋nformed鈥 the blast was from a drone attack.

The IAEA, announcing the incident on the social platform X, gave no further details but its information presumably came from Russians occupying and running the plant since the early stages of the war. 

The Zaporizhzhia Nuclear Power Plant is one of the 10 biggest nuclear plants in the world, and fighting in the southern part of Ukraine where it is located has raised the spectre of a potential nuclear disaster like the one at Chernobyl in 1986, where a reactor exploded and blew deadly radiation across a vast area.

Neither side has in recent months been able to make significant advances along the 1,000-kilometre (620-mile) front line crossing eastern and southern Ukraine. Drones, artillery and missiles have featured heavily in what has become a war of attrition.

Russia and Ukraine have frequently traded accusations over the Zaporizhzhia plant. On Monday, Moscow alleged Ukraine was behind drone attacks on the facility a day before, and Kyiv accused Russia of disinformation tactics.

The IAEA reported Sunday that its inspectors had confirmed 鈥渢he physical impact of drone detonations鈥 and watched as 鈥淩ussian troops engaged what appeared to be an approaching drone.鈥

Energoatom, the Ukrainian nuclear plant operator, blasted Russia鈥檚 latest allegations in a statement Tuesday. It accused Moscow of publishing 鈥減ropaganda鈥 and 鈥渇alse statements鈥 to manipulate public opinion.

It noted that Russia has deployed troops and landmines at the site, which is one of four atomic power plants in Ukraine. The other three remain in Ukrainian hands.

鈥淭he dangerous game of the (Russian) occupiers at the nuclear facility must be stopped,鈥 it said.

The most recent strikes did not compromise the facility, according to the IAEA. But the watchdog has repeatedly expressed alarm about the plant amid fears of a nuclear catastrophe.

The plant鈥檚 six reactors have been shut down for months, but it still needs power and qualified staff to operate crucial cooling systems and other safety features.

According to Ukrainian emergency services, a nuclear disaster would compel the evacuation of some 300,000 people.

Also, Ukraine鈥檚 intelligence agency claimed Tuesday it struck an aviation training centre in southwestern Russia with a drone and said a fire on board a Russian navy corvette on the Baltic coast was 鈥渘ot accidental.鈥

The claims could not be independently verified or corroborated. Russia made no comment on them.