Chernobyl, Ukraine - Ukrainian President Volodymyr Zelensky said on Friday that Russia's military struck the site of the former Chernobyl nuclear power plant.

Zelensky said a Russian drone used a high-explosive warhead to damage the protective cover around the plant, the site of the world's worst nuclear disaster almost 40 years ago.

The structure prevents radiation from leaking from the fourth reactor, which suffered a catastrophic explosion on April 26, 1986.

A fire that erupted following the drone attack has been extinguished and radiation levels have so far not increased, Zelensky said.

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The UN's nuclear agency, which maintains a presence at Chernobyl, said Friday's blast struck late on Thursday night. It posted pictures of a small fire burning on the protective cover.

"This shelter was built by Ukraine together with other countries of Europe and the world, together with America – all those committed to real security for humanity," Zelensky wrote on X.

"The only country in the world that attacks such sites, occupies nuclear power plants, and wages war without any regard for the consequences is today’s Russia. This is a terrorist threat to the entire world."

The Kremlin on Friday denied responsibility for the incident.

The Chernobyl nuclear disaster in the Soviet Union sent radioactive fallout into the air over Europe in what was the largest nuclear accident in history.

Due to the radioactive radiation, an exclusion zone within a radius of around 18 miles was established around the accident site.

During the launch of their full-scale invasion of Ukraine in February 2022, Russian troops nevertheless used the largely deserted restricted area along the Belarusian border to advance on the Ukrainian capital Kyiv.