Russia attacks were reported across large areas of Ukraine on Thursday, with heavy shelling in numerous regions damaging infrastructure, including power supplies to Europe’s largest nuclear power plant, Ukrainian officials said.

The Zaporizhzhia nuclear power plant in southern Ukraine has again been disconnected from the power grid after Russian shelling damaged the remaining high voltage lines, leaving it with just diesel generators, Ukraine nuclear firm Energoatom said.

The plant, in Russian hands but operated by Ukrainian workers, has 15 days’ worth of fuel to run the generators, Energoatom said.

Russian strikes were also reported in Kriviy Rih, in central Ukraine, and in Sumy and Kharkiv, in the northeast. Heavy fighting was ongoing in the eastern regions of Luhansk and Donetsk.

“The enemy is trying to keep the temporarily captured territories, concentrating its efforts on restraining the actions of the Defence Forces in certain areas,” Ukraine’s general staff said on Thursday.

Russia has said it targeted infrastructure as part of what it calls its “special military operation” to degrade the Ukrainian military and remove what it says is a potential threat to Russia’s security.

As a result, Ukrainian civilians have endured power cuts and reduced water supplies in recent weeks. Russia denies targeting civilians, though the conflict has killed thousands, displaced millions and left some Ukrainian cities in ruins.