KYIV, Ukraine (AP) — Russia resumed shelling near Ukraine’s Zaporizhzhia nuclear power plant, a local official said Wednesday, a day after the UN atomic watchdog agency pressed for the warring sides to carve out a safe zone there to prevent a catastrophe.

The city of Nikopol, on the opposite bank of the Dnieper River from Europe’s largest nuclear plant, was fired on with rockets and heavy artillery, regional Governor Valentyn Reznichenko said. The report could not independently verified.

“There are fires, blackouts and other things at the (plant) that force us to prepare the local population for the consequences of the nuclear danger,” Reznichenko said. Officials in recent days have distributed iodine pills to residents to help protect them in the event of a radiation leak.

The fighting going on around the plant has caused international alarm.

The head of the UN’s International Atomic Energy Agency, Rafael Grossi, warned the UN Security Council on Tuesday that “something very, very catastrophic could take place” at Zaporizhzhia. The IAEA urged Russia and Ukraine to establish a “nuclear safety and security protection zone” around the plant.

The fear is that the fighting could trigger a disaster on the scale of the Chernobyl disaster in Ukraine in 1986.

Neither Moscow nor Kiev officials would immediately commit to the idea of a safety zone, saying more details of the proposal were needed.

Because of damage from the fighting, the plant is generating electricity only to power its safety systems, a senior Ukrainian official said. The plant normally relies on external power to run the systems that keep the reactor cores cool and prevent them from melting down.

Any further disruption of power could force the plant to use back-up diesel generators, but that would entail bringing four diesel trucks a day through the fighting, said Oleh Korikov, Ukraine’s acting chief inspector for nuclear and radiation safety.

“We could potentially be in a situation where we run out of diesel,” he said. “And this can lead to an accident with damage to the active zone of the reactors and, accordingly, the release of radioactive products into the environment.”

The plant also had to activate its diesel generators late last month because of damage, according to Ukrainian authorities.

Authorities could consider shutting down the plant, Korikov said, without offering details about how that would work.

The plant’s operator, Energoatom, said that despite the shelling, Ukrainian staff still working at the Russian-occupied plant will try in the coming days to restore the supply of external power through at least one of the seven outside lines.

In other developments, Russian President Vladimir Putin defied pressure to halt the war, saying Moscow will forge ahead with its offensive in Ukraine until it achieves its goals. He mocked Western attempts to stop Russia with sanctions.

Heavy fighting was reported on three fronts: in the north, near the city of Kharkiv; in the east, in the industrial Donbas region of mines and factories; and in the south, in the Kherson region, where Ukraine has mounted a counteroffensive to try to retake territory seized by the Russians early in the war.

Ukrainian forces have taken control of an unspecified number of towns in the Kherson region, military spokesperson Nataliya Humenyuk said.

The eastern city of Sloviansk came under Russian fire on Wednesday morning, and a school and another building were damaged, according to the head of the city administration, Vadym Lyakh.

Firefighters dug deep into the smoldering rubble of an apartment building and removed at least one body. Chunks of bricks, masonry and concrete lay among torn tree branches, broken glass and roof tiles. Metal doors, buckled by the force of the blast, hung off their hinges.

The strike came at around 4 a.m., said resident Raisa Smelkova, 75, who lives in another part of the building. She and her husband were unhurt. The couple lived through the fighting in Ukraine in 2014, when Russia annexed the Crimea region.

“What is happening now is not just scary, it’s gruesome,” she said. “There is more destruction. Everything is worse. Just everything.”

The Russian military held large-scale military drills that began last week and ended Wednesday in the country’s east that involved forces from China. It was seen as another show of increasingly close ties between Moscow and Beijing amid tensions with the West over the war.