The disruption came during a fresh wave of Russian strikes across Ukraine which killed at least nine people and led to power outages across the country.

"The last power line between the occupied Zaporizhzhia NPP and the Ukrainian power system was cut off as a result of rocket attacks," Energoatom said.

The operator said it was the sixth time that the facility had been disconnected from the electricity grid since Russian forces captured the plant last year.

The plant is being powered by diesel generators, which can provide the facility's energy needs for 10 days, Energoatom added.

"The countdown has begun. If it is impossible to renew the external power supply of the station during this time, an accident with radiation consequences for the whole world may occur," Energoatom said.

Russian authorities that control the plant said diesel generators had been switched on following a "short-circuit" on power lines, without providing details.

"There are enough fuel reserves to ensure the operation of generators," they said in a statement, adding that all safety and security issues at the plant were in order.

Moscow's troops seized the plant on March 4, 2022, just days after invading Ukraine.

Moscow and Kyiv have accused each other of shelling around Zaporizhzhia, the biggest nuclear facility in Europe.

The UN's nuclear agency IAEA deployed observers to the plant in September and is seeking to negotiate a demilitarised zone near the facility, but talks appear to have stalled.