Overnight shelling that cut the power line supplying cooling systems at the Russian-held Zaporizhzhia nuclear power plant in Ukraine was “tremendously irresponsible,” the UN atomic watchdog said on Saturday, calling again for a protection zone.

“The resumption of shelling, hitting the plant's sole source of external power, is tremendously irresponsible,” the International Atomic Energy Agency quoted its chief Rafael Grossi as saying, confirming that the plant is now relying on diesel generators.

Grossi would visit Russia and Ukraine “soon” to discuss setting up a protection zone at the plant, it added.