A state-run Russian nuclear energy company accused Ukraine of striking the cooling tower of the Novovoronezh nuclear power plant with a drone overnight into Tuesday.

Newsweek has contacted the Ukrainian Air Force for comment.

Rosenergoatom, which operates the nuclear plant, said in a statement posted to Telegram that the drone “detonated” after being “suppressed by technical means” and colliding with the cooling tower.

The incident highlights the severe nuclear risks posed by the war between Russia and Ukraine, with both sides hosting nuclear power plants affected by the fighting.

“There were no damages or casualties; however, a dark mark remained on the cooling tower from the detonation’s effects,” Rosenergoatom said in its statement, originally in Russian.

“The safe operation of the nuclear power plant is ensured. The radiation background at the Novovoronezh NPP industrial site and the surrounding area has not changed and remains at natural levels. Law enforcement agencies are working at the site.”

It said the plant’s operations were unaffected.

“This is yet another act of aggression by the Ukrainian Armed Forces against Russian nuclear power plants. Earlier, there had been attempts to strike key facilities of the Kursk and Smolensk NPPs,” the Rosenergoatom statement said.

Newsweek has contacted the International Atomic Energy Agency (IAEA) for comment.

Ukraine has previously accused Russia of reckless attacks around its nuclear sites, such as at Zaporizhzhia—currently occupied by Russia—and Chernobyl.

“Russia is deliberately creating the threat of radiation incidents,” Ukrainian President Volodymyr Zelenskyy said late Wednesday after a Russian attack on the energy grid left the Chernobyl nuclear plant without power for several hours.

This is a breaking news story. Updates to follow.