Shelling around the Russian-controlled Zaporizhzhia power plant in southern Ukraine has raised fears of a nuclear disaster.

The International Atomic Energy Agency (IAEA), which has two experts at the plant since a mission there early this month, has urged fighting around the facility to stop.

"What we need here really is Ukraine and Russia to agree on a very simple principle of not attacking or not shelling the plant," IAEA director general Rafael Grossi told reporters.

"Basically it's a commitment that no military action will include or will imply aiming of course at the plant or a radius that could be affecting its normal operation. This is what we expect."

He added both Kyiv and Moscow were "engaging" with the agency on the issue and asking "lots of questions".

"I have seen signs that they are interested in this agreement," Grossi said after he opened the Vienna-based agency's regular 35-member Board of Governors meeting.

Kyiv insists Russian forces must withdraw from the plant, but Grossi said "areas that have to do with larger demilitarisation or movements of troops, none of that is part of my mandate".

Later on Monday, the spokesman for Ukraine's foreign ministry reiterated that "the only way to ensure the nuclear safety and security of the Zaporizhzhia power plant is its de-occupation, demilitarisation and return to Ukrainian control".

"All IAEA efforts must be focused on achieving this goal. Anything short of this won't make Russia stop its dangerous game," Oleg Nikolenko wrote on Twitter.

- 'Unsustainable' -

The IAEA Board of Governors meeting this week is expected to pass a resolution urging Russia "to immediately cease" all actions against the Zaporizhzhia plant and "any other" nuclear facility in Ukraine so that "the competent authorities" regain full control, several diplomats told AFP.

Ukraine said Sunday the sixth and final reactor at the Zaporizhzhia power station was shut down.

Grossi said the situation was "stable" for now but warned it was "unsustainable" in the long run if shelling continued.

Both Kyiv and Moscow have blamed each other for the shelling.

French President Emmanuel Macron asked Russian counterpart Vladimir Putin in a telephone call on Sunday to withdraw heavy and light weaponry from the plant, according to Macron's office.

Putin said Russian specialists at the plant were taking steps to ensure its safety and said Moscow was ready to continue work with the IAEA to agree on "non-politicised" solutions to problems at the facility, according to the Kremlin.