Ukraine on Saturday said Russia had launched a "massive" overnight attack on energy infrastructure in the west and south, adding that at least seven people died in strikes elsewhere.
Russia launched 16 cruise missiles from land, sea and air as well as 13 attack drones, aiming at energy infrastructure in several regions, Ukraine's military said.
Air defences downed all but four of them, it added.
The energy ministry said this was "the eighth massive, combined attack on energy infrastructure facilities" in the past three months, targeting the southern Zaporizhzhia region and Lviv in the west.
"Equipment at (operator) Ukrenergo facilities in the Zaporizhzhia and Lviv regions was damaged," the ministry said.
Ukrenergo said that two employees were wounded and hospitalised in Zaporizhzhia, where Europe's biggest nuclear plant is located.
More than two years into the Russian invasion, targeted missile and drone attacks have crippled Ukraine's electricity generation capacity and forced Kyiv to impose blackouts and import supplies from the European Union.
Ukrenergo said outages across the country would start earlier than usual on Saturday, running from 1100 GMT to 2100 GMT due to damage from the attacks.
In Zaporizhzhia, shelling over the last day also killed one civilian and destroyed residential buildings and infrastructure, according to the regional military administration.
Russia controls a part of the region and the nuclear plant. The Russian-appointed administration said Ukrainian attacks had damaged a substation linked to the city's nuclear power plant but did not affect nuclear safety.
Maksym Kozytskyi, the governor of the western Lviv region, said Russia "launched a missile attack on a critical energy infrastructure facility", sparking a fire that was later extinguished.
Ukrainian troops based in the west shot down seven out of 10 cruise missiles fired by Moscow, the Lviv regional governor said.
Five civilians were killed by Russian shelling in frontline areas of the eastern Donetsk region over the last day, the head of the region, Vadym Filashkin said.
Moscow is trying to advance in the area near the town of Pokrovsk, where intense clashes took place on Saturday, Ukraine's military said, adding the situation was "under control".
In the southern Kherson region, a policeman manning a checkpoint was killed by a drone, the national police force said.
Russia's defence ministry said it had hit 340 Ukrainian targets over the past day.
Russian attacks have destroyed half of Ukraine's energy capacity, according to President Volodymyr Zelensky.
Zelensky said this week that all hospitals and schools in Ukraine must be equipped with solar panels "as soon as possible".
"We are doing everything to ensure that Russian attempts to blackmail us on heat and electricity fail," he said Thursday.
DTEK, the largest private energy company in Ukraine, said Thursday that strikes caused "serious damage" at one of its plants.
DTEK chief executive Maxim Timchenko warned that Ukraine "faces a serious crisis this winter" if the country's Western allies do not provide military aid to defend the energy network.
Zelensky has repeatedly urged Ukraine's allies to send more air-defence systems to protect the country's vital infrastructure.
