The nuclear safety and security situation at the Zaporizhzhia Nuclear Power Plant in Ukraine remains "extremely fragile and dangerous," said the chief of the International Atomic Energy Agency (IAEA) on Tuesday.

"Military activities continue in the region and may well increase very considerably in the near future," IAEA Director General Rafael Grossi told a UN Security Council briefing.

The plant has been operating on significantly reduced staff, which despite being in temporary shutdown is not sustainable, he said.

There have been seven occasions when the site lost all off-site power and had to rely on emergency diesel generators, the last line of defense against a nuclear accident, to provide essential cooling of the reactor and spent fuel. The last one, the seventh, occurred just one week ago, Grossi said.

"We are fortunate that a nuclear accident has not yet happened... we are rolling a dice and if this continues then one day our luck will run out," he warned.

"So we must all do everything in our power to minimize the chance that it does," said Grossi, then laying out five principles to safeguard the plant.

The principles included that there should be no attack on or from the plant and that no heavy weapons such as multiple rocket launchers, artillery systems and munitions, and tanks or military personnel be housed there.

Grossi also called for off-site power to the plant to remain available and secure; for all its essential systems to be protected from attacks or sabotage; and for no actions that undermine these principles.

"Mr Grossi's proposals to ensure the security of the Zaporizhzhia nuclear power plant are in line with the measures that we've already been implementing for a long time," Russia's UN Ambassador Vassily Nebenzia said.

Ukraine's ambassador to the UN, Mr Sergiy Kyslytsya, said the principles "must be complemented with the demand of full demilitarization and deoccupation of the station."

Russia and Ukraine have blamed each other for shelling that has repeatedly downed power lines vital to cooling the reactors, which are shut down but need a constant supply of electricity to keep the nuclear fuel inside cool and prevent a possible meltdown.

(With input from agencies)