Ukraine was scrambling to turn lights and heating back on Sunday after Russian attacks targeting energy infrastructure reduced the country’s power generating capacity to “zero”.

Moscow, which has escalated attacks on Ukraine’s infrastructure in recent months, launched hundreds of drones at energy facilities across the country overnight into Saturday.

The attacks interrupted electricity, heat and water supplies in several cities, with state power firm Centerenergo warning generating capacity “is down to zero”.

Power would be cut for between eight and 16 hours a day across most regions of Ukraine on Sunday, state provider Ukrenergo said, while repairs were carried out and energy sourcing diverted.

While the situation had somewhat stabilised, regions including Kyiv, Dnipropetrovsk, Donetsk, Kharkiv, Poltava, Chernigiv and Sumy could continue to see regular power cuts, Ukraine’s energy minister said on Saturday evening.

“The enemy inflicted a massive strike with ballistic missiles, which are extremely difficult to shoot down. It is hard to recall such a number of direct strikes on energy facilities since the beginning of the invasion,” Svitlana Grynchuk told local broadcaster United News.

Russian drones had targeted two nuclear power substations deep in western Ukraine, Kyiv’s Foreign Minister Andrii Sybiha said, calling on the UN’s nuclear watchdog to respond.