"The current situation is untenable," the UN atomic watchdog said in a report after it sent a team to the plant last week.

The occupation of the nuclear power plant, Europe's largest, has sparked fears of a nuclear disaster as both sides trade blame for shelling the site.

"There is an urgent need for interim measures to prevent a nuclear accident arising from physical damage caused by military means," the IAEA said.

"This can be achieved by the immediate establishment of a nuclear safety and security protection zone," it added in its report.

"The IAEA recommends that shelling on site and in its vicinity should be stopped immediately to avoid any further damages to the plant and associated facilities," it said.

The UN agency sent a 14-person team to the site last week, including Rafael Grossi, to assess the situation at the plant.

At least two members of the team were to remain there on a permanent basis to ensure the facility's safety.

Russian troops seized control of the site in early March and there have been repeated attacks in the vicinity.

Both Moscow and Kyiv have denied responsibility.

The IAEA said Saturday the plant had been disconnected from its last remaining main power line to the grid and was relying on a reserve line.