CHERNOBYL NUCLEAR POWER STATION, Ukraine (AP) — A drone armed with a warhead hit the protective outer shell of Ukraine’s Chernobyl nuclear plant early Friday, damaging the structure and briefly starting a fire, in an attack Kyiv blamed on Russia. The Kremlin denied it was responsible.

Radiation levels at the shuttered plant in the Kyiv region — site of the world’s worst nuclear accident — have not increased, according to the U.N. International Atomic Energy Agency, which said the strike did not breach the plant’s inner containment shell.

The IAEA did not attribute blame, saying only that its team stationed at the site heard an explosion and was informed that a drone had struck the shell.

Fighting around nuclear power plants has repeatedly raised fears of a nuclear catastrophe during three years of war, particularly in a country where many vividly remember living through the 1986 Chernobyl disaster, which killed at least 30 people and spewed radioactive fallout over much of the Northern Hemisphere.

The Zaporizhzhia nuclear power plant, which is Europe’s biggest, has occasionally been hit by drones during the war without causing significant damage.

The strike came two days after President Donald Trump upended U.S. policy on Ukraine, saying he would meet with Russian President Vladimir Putin to discuss ending the war. The move seemed to identify Putin as the only player that matters and looked set to sideline Ukrainian President Volodymyr Zelenskyy, as well as European governments, in any peace talks.

The hit on Chernobyl occurred as Ukraine is being slowly pushed back by Russia’s bigger army along parts of the 1,000-kilometer (600-mile) front line and is desperately seeking more Western help.

Zelenskyy said a Russian drone with a high-explosive warhead hit the plant’s outer shell and started a fire, which has been put out. The shell was built in 2016 over another heavy concrete containment structure, which was placed on the plant’s fourth reactor soon after the 1986 disaster. Both shells seek to prevent radiation leaks.

The Ukrainian Emergency Service provided a photograph that showed a hole punched in the roof of the outer shell, which is a massive steel-and-concrete structure weighing some 40,000 tons (36,000 metric tons) and tall enough to fit Paris’ Notre Dame Cathedral inside.

Kremlin spokesman Dmitry Peskov denied Russia was responsible. “There is no talk about strikes on nuclear infrastructure, nuclear energy facilities. Any such claim isn’t true. Our military doesn’t do that,” Peskov said in a conference call with reporters.

It was not possible to independently confirm who was behind the strike. Both sides frequently trade blame when nuclear sites come under attack.

Peskov alleged that the strike was a “false flag” attack staged by Ukraine to incriminate Russia and to thwart efforts to end the war through negotiations between Trump and Putin.

“It’s obvious that there are those (in the Ukrainian government) who will continue to oppose any attempts to launch a negotiation process, and it’s obvious that those people will do everything to try to derail this process,” Peskov said.

Russian Foreign Ministry spokesperson Maria Zakharova described the drone attack as a “reckless” act by Kyiv and noted that Russia had been part of the international effort to build the structure that was hit.

Ukraine plans to provide detailed information to U.S. officials about the Chernobyl strike during the Munich Security Conference starting Friday, the head of Ukraine’s Presidential Office, Andrii Yermak, wrote on his Telegram channel.

IAEA chief Rafael Grossi said on X that the strike and the recent increase in military activity near Zaporizhzhia “underline persistent nuclear safety risks,” adding that the IAEA remains “on high alert.”

The IAEA said its personnel at the site responded within minutes of the strike, adding there were no casualties.

“Radiation levels inside and outside remain normal and stable,” the IAEA said on X.

Zelenskyy said on Telegram that the Chernobyl strike showed that Putin “is certainly not preparing for negotiations” — a claim Ukrainian officials have repeatedly made.

“The only state in the world that can attack such facilities, occupy the territory of nuclear power plants, and conduct hostilities without any regard for the consequences is today’s Russia. And this is a terrorist threat to the entire world,” he wrote.

“Russia must be held accountable for what it is doing,” he added.

Novikov reported from Kyiv, Ukraine.