Around a dozen strikes had targeted the plant, he said, and the situation was "very serious", the head of the International Atomic Energy Agency (IAEA) told French broadcaster BFMTV.

It was an outrage that some people "consider a nuclear power plant to be a legitimate military target", he said.

While he did not blame either Russia or Ukraine, Grossi said: "Whoever it is, stop this madness!

"The people who are doing this know where they are hitting. It is absolutely deliberate, targeted."

Earlier Sunday, Kyiv and Moscow blamed each other for shelling the site of the Zaporizhzhia nuclear power plant in southern Ukraine.

The IAEA is to send a team of experts to the plant -- the biggest nuclear facility in Europe -- after the "powerful explosions" there on Saturday and Sunday.

"The plant is on the front line, there are military activities that are very difficult to identify, there are Russian troops and Ukrainian troops in operation," Grossi said.

"There has been damage in some rather delicate places," he added, though the nuclear reactors themselves have not been affected but "rather the area where the fresh and spent fuel is located.

"We expect to be able to take stock of the situation very early tomorrow morning," he added. But the inspectors had not been able to leave for the site on Sunday, as the situation was too dangerous, he said.

Russia, which launched an offensive in Ukraine in February, has been occupying the territory around the power station. Russian President Vladimir Putin has claimed its annexation, along with that of four Ukrainian regions.

Moscow and Kyiv have for blamed each other for the repeating shelling of the site.