The International Atomic Energy Agency says shelling has once again cut off external power supplies to Ukraine's Zaporizhzhia nuclear power plant.

IAEA Director General Rafael Mariano Grossi issued a statement on Saturday. He said that emergency diesel generators are cooling the reactors. Each of the plant's six reactors is reportedly in a state of cold shutdown.

The statement says engineers at the plant have begun work to repair the damaged power line. It adds that the plant's safety systems are operating normally.

The Russian-occupied nuclear plant has repeatedly lost external power due to shelling. That has raised serious concerns about the facility's safety.

In the statement, Grossi said, "The resumption of shelling, hitting the plant's sole source of external power, is tremendously irresponsible." He added that the plant must be protected.

Grossi said he will visit Russia soon. He said he wants to reach an agreement on the establishment of a "nuclear safety and security protection zone" around the plant.