Russian attacks were reported in several areas of Ukraine on Thursday, with heavy shelling in many regions damaging infrastructure, including power sources for Europe’s largest nuclear power plant, Ukrainian officials said, Reuters reported.

The Zaporizhia nuclear power plant in southern Ukraine has been disconnected from the power grid again after Russian bombing damaged the remaining high-voltage power lines, leaving only diesel generators on it, Ukrainian nuclear company Energoatom said.

The nuclear power plant, which is under Russian occupation but is serviced by Ukrainian workers, has a supply of fuel to operate the generators for 15 days, Energoatom reported.

There are also reports of Russian strikes in Kryvyi Rih in central Ukraine, as well as in Sumy and Kharkiv in the northeast. Heavy fighting is taking place in the eastern regions of Luhansk and Donetsk regions.

“The enemy is trying to hold the temporarily captured territories, focusing efforts on limiting the actions of the defense forces in certain areas,” the General Staff of Ukraine reported on Thursday.

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

As a result, Ukrainian civilians have experienced power outages and reduced water supplies in recent weeks. Russia denies attacks on civilians, even though the conflict has killed thousands, displaced millions and left some Ukrainian cities in ruins.