Ukraine and Russia blamed each other for strikes that caused the damage. The BBC was not able to independently verify which side was responsible.

Russia's military took over the plant in early March, but it is still being operated by Ukrainian staff under difficult conditions.

The Kremlin had previously signalled that it would only allow international inspectors to visit the complex so the IAEA's visit will mark an important moment in being able to verify what is happening on the ground.

Ukraine had feared an IAEA mission to Zaporizhzhia would legitimise the Russian occupation of the nuclear plant, before finally backing a visit.

"Almost every day there is a new incident at or near the Zaporizhzhia nuclear power plant. We can't afford to lose any more time," the IAEA director general said.

Experts say shelling around the plant is not the main concern, given the plant has thick protection walls.

However, cutting the supply of electricity to it is fraught with danger. The loss of the power supply to the nuclear reactors and back-up generators would mean no power for the pumps cooling the hot reactor core and therefore leading to the fuel starting to melt.