Russia has launched the largest attack on Ukraine's energy infrastructure since the spring, primarily targeting Kyiv and the surrounding region, Ukrainian Prime Minister Serhiy Koretskyi has said.
At least five people were killed in overnight attacks across the country, including a child in the Kyiv region, Koretskyi said.
The strikes also impacted people's power supplies, with Ukraine's biggest private energy firm, DTEK, saying power to 8,000 homes had been restored following "a difficult night" for the capital.
The Russian defence ministry said one of its targets was the Trypilska power station, the largest supplier of electricity to Kyiv.
In a statement on Telegram, Koretskyi said: "Since the summer, there has effectively not been a single day without enemy attacks on our energy infrastructure.
"However, a mass and combined attack of this scale has occurred for the first time since the end of the last heating season."
Ukraine has been expecting another protracted Russian assault on the country's energy grid. It has happened every winter so far since Russia's full-scale invasion in 2022.
In total 11 regions of the country were attacked overnight, with residential buildings, social infrastructure, civilian enterprises and railways also targeted, Koretskyi said.
Ukrainian President Volodymyr Zelensky said there were strikes on critical infrastructure in the Zhytomyr, Mykolaiv, Kirovohrad and Rivne regions.
On Wednesday, some households in the Kyiv, Dnipropetrovsk, Donetsk, Sumy, Kyiv and Kharkiv regions remained without power, Ukraine's energy ministry said.
State-owned grid operator Ukrenegro advised residents not to use powerful electrical appliances between the hours of 10:00 and 16:00 local time as electricity supplies were lower than usual.
Russia's defence ministry said it had launched massive overnight strikes on Ukrainian facilities.
It said its targets included the Trypilska thermal power plant, located some 40km from Kyiv, and claimed the plant supplied electricity to Ukrainian defence facilities.
The operator of the plant, Centrenergo, confirmed that the plant had been damaged in a Russian attack and that it was assessing the scale of the damage.
In Kyiv, people woke to find the city blanketed by thick, acrid smoke after a night punctuated by the sound of explosions. An air raid alert was still on and the distant sound of air defence gunfire echoed through the murky atmosphere.
Residents in several districts were advised to close their windows until the smoke cleared.
Among those killed in the overnight strikes was a child whose body was found under the rubble of a house, Kyiv regional governor Timur Tkachenko said.
Kyiv Mayor Vitaly Klischko said three people were killed in total in the capital, including a Ukrainian utility company worker who was killed at a warehouse building.
Another person was killed in the Mykolaiv region, acting regional governor Heorhiy Reshetilov said.
Two more people were also killed in the north-eastern Sumy region on Tuesday, governor Oleh Hryhorov said. A school was also hit there in a separate strike, he added.
Russian President Vladimir Putin launched a full-scale invasion of Ukraine in 2022, and Moscow currently controls about 20% of Ukrainian territory.
