"We are aware of the current situation. There has been military activity, including this morning, several minutes ago.. but we are not stopping," IAEA chief Rafael Grossi told reporters.

His remarks came as Ukraine accused Russia of firing on Energodar, the town next to the plant which is about a two-hour drive from Zaporizhzhia.

"We know there is a grey area where the last line of Ukrainian defence and the first line of the Russian occupying forces begins, where the risks are significant," Grossi said shortly before the team left to cross the frontline into Russian-held territory.

"I believe we have to proceed with this. We have a very important mission to accomplish."

An AFP team saw them leave Zaporizhzhia city at around 8:15 am (0515 GMT).

Energodar lies on the south side of the Dnipro River, with Mayor Dmytro Orlov saying the town of 50,000 had come come under sustained attack since dawn, when Russian troops had "shelled Energodar with mortars and used automatic weapons and rockets".

In a posting on Telegram, he published photos of damaged buildings in the Russian-occupied territory with smoke spiralling above them.