MOSCOW, Apr. 7 (Reuters) - Russia's nuclear power corporation, Rosatom, accused Ukraine's military on Sunday of launching a series of attacks on the Russian-held Zaporizhzhia nuclear power station and the U.N.'s nuclear watchdog called for such incidents to cease immediately.

Rosatom said three people were hurt, one seriously. Russia urged world leaders to denounce the incidents. Both Russian officials and the U.N.'s International Atomic Energy Agency said radiation levels were normal and damage not severe.

A Ukrainian intelligence official said Kyiv had nothing to do with any strikes on the station, the largest in Europe, and suggested they were the work of Russians themselves.

Reuters was unable immediately to verify battlefield accounts from either side.

Russian troops seized the plant in the first weeks of the February 2022 invasion of Ukraine. Each side accuses the other of attacking the plant, which lies close to the front lines of the 25-month-old conflict, and risking a nuclear disaster.

A Rosatom statement said the first strike on the plant hit an area near a canteen, injuring the three staff members, but did not indicate what weapon had been involved.

Within a half hour, it said, a drone had attacked a cargo loading area and another drone subsequently struck the dome of the sixth reactor.

The statement said Rosatom "categorically denounces the unprecedented attack" and called on IAEA chief Rafael Grossi and the European Union to immediately react to the threat to safety.

Russian Foreign Ministry spokeswoman Maria Zakharova urged world leaders to condemn the act of "nuclear terrorism."

"How many more times must the Ukrainian military target the Zaporizhzhia plant in order for the West and that monster Zelenskiy, nurtured by them, to stop repeating this deadly act of their bloody circus?" she wrote on Telegram, referring to Ukraine's president, Volodymyr Zelenskiy.

A spokesperson for Ukraine's HUR Main Intelligence Directorate, Andriy Usov, denied any involvement.

"Russian strikes, including imitation ones, on the territory of the Ukrainian nuclear power plant ... have long been a well known criminal practice of the invaders," he wrote on Telegram.

The IAEA, which has experts at the site, reported on social media platform X that there had been a single casualty.

"Damage at unit 6 has not compromised nuclear safety, but this is a serious incident w/ potential to undermine integrity of the reactor's containment system," the agency said.

The IAEA's Grossi added there had been three "direct hits" to such structures.

"This cannot happen," he wrote.

The nuclear plant has six Soviet-designed VVER-1000 V-320 water-cooled and water-moderated reactors containing Uranium 235, and also has spent nuclear fuel at the facility.

Reactors 1, 2, 5 and 6 are in cold shutdown, while Reactor No. 3 is shut down for repair and Reactor No. 4 is in so-called hot shutdown, according to the plant.

Photo from Reuters