"As a result of periodic shelling, the infrastructure of the station has been damaged, there are risks of hydrogen leakage and sputtering of radioactive substances, and the fire hazard is high," Energoatom said on Telegram.

After Thursday the plant was cut off from the electrical grid for the first time it its history, which was subsequently restored hours later, there's been growing international alarm over the potential for a Chernobyl-style disaster. 

Energoatom further claimed that Russian troops "repeatedly shelled" key infrastructure at the plant - a charge rejected by Moscow. Instead Russia's defense ministry countered that it was the Ukrainian side that  "shelled the territory of the station three times" in the past day, saying "a total of 17 shells were fired."

The agency further warned the plant "operates with the risk of violating radiation and fire safety standards" - in the statement which came midday Saturday (local time).

Ukrainian authorities are calling for international intervention due to the continued instability of the situation. "Due to the presence of the Russian military, their weapons, equipment and explosives at the power plant, there are serious risks for the safe operation of the ZNPP," Energoatom said.