There are no immediate nuclear safety or security concerns at the Russian-held Zaporizhzhia nuclear power plant in Ukraine despite shelling at the weekend that caused widespread damage, the UN atomic watchdog said after its experts toured the site.

The International Atomic Energy Agency, which has four of its staff based at Zaporizhzhia, Europe's biggest nuclear power plant, said on Sunday there had been some of the heaviest shelling in recent months there this weekend, though it added that key nuclear safety and security systems had not been hit.

Russia and Ukraine have blamed each other for shelling at the plant in recent months that has damaged buildings and knocked out power lines supplying the plant that are crucial to cooling the six reactors' fuel and avoiding a nuclear meltdown. Those lines were not affected by this weekend's shelling.

"They (IAEA experts) were able to confirm that – despite the severity of the shelling – key equipment remained intact and there were no immediate nuclear safety or security concerns," the International Atomic Energy Agency said in a statement issued on Monday evening.

"The status of the six reactor units is stable, and the integrity of the spent fuel, the fresh fuel and the low, medium and high-level radioactive waste in their respective storage facilities was confirmed," the IAEA said, adding that there was "widespread damage across the site".

That damage included "several impacts on the main road along the plant's reactors", shrapnel hitting a pressurised air pipeline, "minor visible damage to a sprinkler charging pipeline" and damage to the roof of what it called a special auxiliary building.

"This is a major cause of concern as it clearly demonstrates the sheer intensity of the attacks on one of the world’s largest nuclear power plants," the statement quoted IAEA chief Rafael Grossi as saying.

Grossi has been warning for months of the risk of a potentially catastrophic accident because of the shelling and is pushing for a protection zone around the plant. The IAEA said he had "intensified his consultations" on the protection zone after this weekend's shelling. (Reuters)