In a statement Rafael Grossi, director general of the International Atomic Energy Agency (IAEA), said that the strikes represented "the latest in a long line of increasingly alarming reports" and underlined "the very real risk of a nuclear disaster that could threaten public health and the environment in Ukraine and beyond".

Earlier on Saturday the plant's operator said Friday's shelling had "seriously damaged" a station containing nitrogen and oxygen and an "auxiliary building".

Ukraine and Russia have blamed each other for the attacks.

Grossi said: "I condemn any violent acts carried out at or near" the plant or against its staff.

He added that "military action jeopardising the safety and security" of the plant was "completely unacceptable and must be avoided at all costs".

Grossi also reiterated his willingness "to lead a mission of IAEA safety, security and safeguards experts" to Zaporizhzhia.

Ukraine has so far rejected the idea of such a mission, which it says would legitimise Russia's presence at the site.

Russian troops have occupied the Zaporizhzhia plant since the early days of their invasion of Ukraine.

However, Grossi insisted that he would "not give up".

"I will continue to push and push again for this IAEA mission to finally take place," he said, while admitting that it would require "cooperation, understanding and facilitation from both Ukraine and Russia".

As part of such a mission "IAEA safeguards inspectors could conduct essential verification activities at the plant" and the IAEA "would also provide impartial and independent information" about the status of the plant, Grossi said.