Ukraine's state-owned power company says the Russian-occupied Zaporizhzhia nuclear power plant temporarily lost external power early on Saturday as a result of disconnection with power lines.

Workers used an emergency generator to maintain the cooling system from the early hours until power was restored later in the morning.

The reason behind the outage was not immediately clear.

The International Atomic Energy Agency says it was the eighth time since Russia's invasion began that Europe's largest nuclear power plant has suffered a complete off-site power outage. The last time was in May.

IAEA Director General Rafael Grossi said in a statement the incident is "yet another reminder about the precarious nuclear safety and security situation at the plant."

He called on all parties to refrain from any action that could further endanger the plant.