Europe's largest nuclear facility fell to Russian forces shortly after the invasion of Ukraine in February 2022, and Kyiv and Moscow have repeatedly accused each other of planning an incident at the site.

"Mines along the perimeter of the ZNPP (Zaporizhzhia Nuclear Power Plant)... are now back in place," said the International Atomic Energy Agency (IAEA) in a statement.

The mines, previously identified by agency experts on site, had been removed in November, but are now back, which is "inconsistent with the IAEA safety standards," the statement added.

They are in "a restricted area inaccessible to operational plant personnel" in a buffer zone between the facility's internal and external fences, it added.

The IAEA added that its experts had not been granted access to several reactor halls, as well as some other areas.

"Such access is needed to monitor nuclear safety and security," the statement said.

The experts were granted access to the reactor hall of one of the units earlier this week.

Earlier this month, Russia said it was blocking access for safety reasons.

IAEA head Rafael Grossi has repeatedly warned of "persistent nuclear safety and security risks at the site".

IAEA officials have been on the ground monitoring the plant since September 2022.

The plant has been repeatedly rocked by shelling and drone attacks near it throughout the conflict.

It has also been severed from the grid several times, raising fears of a major nuclear accident.

The six reactor units, which before the war produced around a fifth of Ukraine's electricity, have been shut down.

But it still needs electricity and water to cool its systems.