The U.N.'s nuclear watchdog said on Thursday that officials at Ukraine's Russian-held Zaporizhzhia nuclear power plant had reported a new attempted drone attack on the facility's training centre -- less than two weeks after other similar incidents.

Russia-installed officials at the plant, the largest nuclear facility in Europe, said Ukraine was behind the latest incident.

Russian forces occupied the plant in the first weeks of the February 2022 invasion of Ukraine and each side has since repeatedly accused the other of attacking the plant.

Rafael Grossi, director general of the International Atomic Energy Agency (IAEA), has warned that attacks and incidents at the plant are "reckless" and could trigger a major nuclear accident.

Grossi said the latest incident had caused no damage or injuries. The IAEA's monitors stationed at the power plant, he said in a statement, had heard an explosion at the same time as the Russia-installed team reported an attempted Ukrainian drone attack.

"If confirmed, it would be an extremely worrying development," Grossi said.

"Whoever is behind these incidents, they appear to be ignoring the international community's repeated calls for maximum military restraint to avert the very real threat of a serious nuclear accident."

Grossi said IAEA monitors were denied access on security grounds to a training centre where the incident was said to have occurred.

There was no immediate comment on the latest reports from Ukrainian officials. Kyiv has denied any connection with previous incidents and suggested the Russians may have staged them.

Russia-installed officials at the plant said the drone had been destroyed above the roof of the building. They added there had been no damage and that nobody had been injured.

Grossi addressed meetings of the IAEA board and the U.N. Security Council this month in connection with a series of incidents over three days, including what Russian officials described as an April 8 attack on the training centre REUTERS