Ukraine and Russia traded fresh accusations of shelling at the Zaporizhzhia nuclear power plant on Saturday, as its operator warned of a radioactive leak risk at the atomic facility.

The Zaporizhzhia plant in southern Ukraine has been occupied by Russian troops since the opening of the invasion.

Kyiv and Moscow have repeatedly swapped allegations over rocket attacks in the vicinity of the plant -- Europe's largest -- located in the city of Energodar.

On Saturday operator Energoatom said Russian troops "repeatedly shelled" it over the past day.

Russia's defence ministry issued a counter-claim that Ukraine's troops were responsible for a salvo of 17 shells landing on the site.

"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.

The agency said that as of midday Saturday (0900 GMT) the plant "operates with the risk of violating radiation and fire safety standards".

Russia's defence ministry said Ukrainian forces "shelled the territory of the station three times" from the town of Marganets across the Dnipro River.

In a communique the ministry accused Kyiv of "nuclear terrorism" and said shells landed near areas storing fresh nuclear fuel and radioactive waste.

Nevertheless radiation levels at the plant "remain normal" the ministry said.

On Thursday, the plant was cut off from Ukraine's national power grid for the first time in its four-decade history due to "actions of the invaders", Energoatom said.

Ukrainian President Volodymyr Zelensky said the power cut was caused by Russian shelling of the last active power line linking the plant to the network.

It came back online on Friday afternoon but Zelensky warned "the worst case scenario ... is constantly being provoked by Russian forces".

The International Atomic Energy Agency (IAEA) is urging for a mission to the plant "as soon as possible to help stabilise the nuclear safety and security situation there".

Agency head Rafael Mariano Grossi has said he wants to visit the site within days, warning of potential disaster.

Ukraine energy minister adviser Lana Zerkal said an IAEA inspection "is planned for the next week".

But Zerkal told Ukraine's Radio NV late Thursday she was sceptical the mission would go ahead, despite Moscow's formal agreement, as "they are artificially creating all the conditions so that the mission will not reach the site".

Britain's defence ministry said satellite imagery showed an increased presence of Russian troops at the power plant with armoured personnel carriers deployed within 60 metres (200 feet) of one reactor.

Kyiv suspects Moscow intends to divert power from the Zaporizhzhia plant to the Crimean peninsula, annexed by Russian troops in 2014. Washington has warned against any such move.

"The electricity that it produces rightly belongs to Ukraine," State Department spokesman Vedant Patel told reporters, saying attempts to redirect power to occupied areas were "unacceptable".

Russia's invasion of Ukraine -- which this week entered its seventh month -- has also prompted a wider global energy crisis.

Anxiety over gas and oil supply has sent prices soaring and on Friday both Germany and France reported record electricity prices for 2023, more than 10 times higher than for this year.

On Friday the EU presidency vowed to hold an emergency summit to address the crisis as the winter months approach.