A senior Ukrainian official has denied Russian accusations that his country’s army fired exploding drones at Europe’s largest nuclear power plant, which the Kremlin’s forces have been occupying and running in southern Ukraine since shortly after the war began more than two years ago.

Andrii Yusov, the spokesperson for Ukraine’s military intelligence agency suggested there had been no attack, saying Russian forces routinely fabricate strikes on the Zaporizhzhia Nuclear Power Plant. However, the strikes on this occasion were confirmed by UN’s atomic watchdog agency, though it didn’t attribute responsibility for the attack to either side.

The plant has repeatedly been caught in the crossfire since Russia launched its full-scale invasion of Ukraine in February 2022 and seized the facility shortly after. The International Atomic Energy Agency, a UN body, has frequently expressed alarm about the facility amid fears of a potential nuclear catastrophe.

The plant’s 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.

The UN’s atomic watchdog agency on Sunday confirmed drone strikes on one of the plant’s six reactors, causing one casualty. The IAEA team did not observe structural damage to the “systems, structures and components” important to the nuclear safety of the plant, it said. They reported superficial scorching to the top of a reactor dome.

The damage “has not compromised nuclear safety, but this is a serious incident (with the) potential to undermine (the) integrity of the reactor’s containment system,” the IAEA said on X, formerly Twitter.

IAEA chief Rafael Mariano Grossi said the main reactor containment structures took at least three direct hits. “This cannot happen,” he said on X.

Zaporizhzhia is one of four regions that Russia illegally annexed in September 2022.

The Institute for the Study of War, a think tank based in Washington, said Russian authorities are seeking “to use Russia’s physical control over the (plant) to force international organizations, including the IAEA, to meet with Russian occupation officials to legitimize Russia’s occupation of the (plant) and by extension Russia’s occupation of sovereign Ukrainian land.”