UNITED NATIONS -- 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 shut-down 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 defence 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.

The IAEA chief laid out new "concrete principles" which he said are essential to avoid the danger of a catastrophic incident at the Zaporizhzhia plant.

There should be no attack of any kind from or against the plant, in particular targeting the reactors, spent fuel storage, other critical infrastructure or personnel, he said.

Zaporizhzhia should not be used as storage or a base for heavy weapons or military personnel that could be used for an attack from the plant, and off-site power to the plant should not be put at risk, he added.

All structures, systems and components essential to the safe and secure operation of the Zaporizhzhia plant should be protected from attacks or acts of sabotage, Grossi said.