Ukrainian President Volodymyr Zelensky said a Russian drone struck the destroyed nuclear power plant at Chernobyl near Ukraine’s border with Belarus on Thursday night.

Ukraine’s State Emergency Service later said that the radiation background limits remain within normal limits.

“A Russian attack drone with a high-explosive warhead struck the shelter protecting the world from radiation at the destroyed 4th power unit” at the plant, Zelensky said on X.

The concrete shelter that covers the unit was damaged, Zelensky added and a fire was extinguished.

“Radiation levels have not increased and are being constantly monitored.

According to initial assessments, the damage to the shelter is significant,” Zelensky said.

The International Atomic Energy Agency said on X that shortly before 2am local time its team at the Chernobyl site “heard an explosion coming from the New Safe Confinement, which protects the remains of reactor 4 of the former Chernobyl NPP, causing a fire.”

“They were informed that a UAV [drone] had struck the NSC roof,” the IAEA added.

Unit 4 at Chernobyl exploded in 1986, sending extensive clouds of radioactivity across parts of the Soviet Union and Europe.

It was later encased in a concrete and steel sarcophagus.

Altogether, on Thursday night, the Ukrainian military reported that Russia fired 133 drones at Ukraine, 73 of which were shot down and 58 did not reach their targets.

The numbers are broadly in line with the recent average of drone attacks.

It said drones were shot down in 11 regions, covering much of the country.

Zelensky said in his post that the nightly drone attacks on Ukrainian infrastructure meant that Russian President Vladimir Putin “is definitely not preparing for negotiations — he is preparing to continue deceiving the world.”