"Shelling has caused a complete blackout in Energodar (town) and compromised the safe operation of the nearby Zaporizhzhia (nuclear power plant)," IAEA director general Rafael Grossi said in a tweet, calling it a "dramatic development".

"This is completely unacceptable. It cannot stand," he said in a statement, urgently calling for "the immediate cessation of all shelling in the entire area".

"Only this will ensure the security of operating staff and allow the durable restoration of power to Energodar and to the power plant," Europe's largest nuclear power facility, he added.

Grossi said he learned of the shelling on Friday from IAEA staff on the site, evoking the "serious situation that developed last night".

Kyiv on Wednesday called for an international mission to be set up in the Zaporizhzhia nuclear power plant and called for the population to evacuate the area amid fears of a nuclear disaster.

The Zaporizhzhia power plant was occupied by Russian troops in March and has been shelled in recent weeks, with Ukraine and Russia blaming each other for the attacks, raising fears of a nuclear disaster.