Russia said on Monday that shelling of the Zaporizhzhia nuclear power plant risked unleashing a grave nuclear accident and repeated accusations, denied by Kyiv, that Ukrainian forces were to blame.
The Kremlin called on "all countries of the world" to pressure Kyiv into ceasing the attacks, for which Ukraine says Russia is responsible.
The repeated shelling of the plant in southern Ukraine, which flared again at the weekend, has raised concern about the potential for a serious accident just 500 km (300 miles) from Chornobyl, site of the world's worst nuclear disaster in 1986.
Reuters was unable to independently verify which side was responsible for the weekend shelling.
"The plant is at risk of a nuclear accident," Alexei Likhachev, the director general of Russia's Rosatom state nuclear corporation, was quoted as saying by Interfax.
"We were in negotiations with the International Atomic Energy Agency (IAEA) all night," he said.
The power plant, which is under Russian control, was rocked by heavy shelling on Saturday and Sunday, drawing condemnation from the U.N. nuclear watchdog which said such attacks risked a major disaster.
A meltdown of a reactor at the plant or a fire of spent nuclear fuel could send a plume of radionuclides into the air, potentially spreading over a large area of Europe.
"This cannot but cause our concern," Kremlin spokesman Dmitry Peskov told reporters, referring to the shelling. "We call on all countries of the world to use their influence so that the Ukrainian armed forces stop doing this."
The International Atomic Energy Agency (IAEA) said its mission at the plant had reported damage to a radioactive waste and storage building, cooling pond sprinkler systems, an electrical cable to one of the reactors, condensate storage tanks, and to a bridge between another reactor and its auxiliary buildings.
External power supplies were not affected and radiation levels at the plant remained normal, the IAEA said.
Russia's defence ministry said Ukraine's armed forces fired 11 large calibre shells at the plant on Saturday and 12 on Sunday morning, then two more at power lines.
Ukraine's nuclear energy firm Energoatom said the Russian military shelled the plant. It said there had been at least 12 hits on the facility on Sunday.
IAEA Director General Rafael Grossi has proposed the establishment of a nuclear safety and security protection zone around the power station.
Rosatom chief Likhachev said this would only be possible if it was approved by the United States. "I think the large distance between Washington and Zaporizhzhia should not be an argument for the United States to delay the decision on a security zone," Interfax quoted him as saying.
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