Ukraine's Zaporozhye nuclear power plant has been without external backup power for three months, which makes it extremely vulnerable, warned the head of the International Atomic Energy Agency (IAEA), Raphael Grossi.

The plant relies on one remaining operational 750-kilovolt transmission line for external electricity needed for reactor cooling and other essential nuclear and safety functions, the IAEA said. Before the conflict, the power plant had four such transmission lines at its disposal. The overall situation at the power plant remains very uncertain and potentially dangerous, Grossi said.

The fragile electricity situation at the plant remains a source of deep concern and, as the newly formed IAEA principles show, there is a need for increased efforts to ensure a more stable and predictable external supply of electricity, the IAEA chief added. The six-reactor power plant was occupied by Russian forces in March last year.