Ukraine's grid operator Ukrenergo said emergency power cuts were imposed in Kyiv after what the head of Kyiv's military administration, Tymur Tkachenko, said earlier was a short but intense missile attack on the capital early on Tuesday.
DTEK, a private Ukrainian energy company, said the Russian attack heavily damaged equipment at one of its thermal power plants.
Russia has repeatedly targeted Ukraine's power system with missiles and drones since launching its invasion in February 2022, aiming to disrupt electricity and heating supplies in winter, as Ukrainian air defences strain to intercept waves of strikes.
Ukrainian Telegram monitoring channels said about 20 ballistic missiles were launched within about an hour overnight, in what they described as the most sustained strike so far in 2026.
Reuters could not independently verify the reports.
Ukraine's armed forces did not immediately comment on the full scale of the attack.
There was no comment from Russia about the strikes.
In Kharkiv, 30km from the border with Russia and also a frequent Moscow target, regional governor Oleh Syniehubov said four people had died in a strike on the outskirts of the city.
Syniehubov said six people were injured.
Ukraine's State Emergency Service said the Kharkiv attack hit a postal terminal, destroying buildings and sparking multiple fires across about 500 square metres.
Rescuers pulled 30 people to safety, including two from under rubble, it said.
In the southern port city of Odesa, five people were injured as a result of the overnight Russian attack, the service said.
It reported fires at an unused new building, a fitness centre and a vocational school.
Two people were injured as a result of a Russian attack on the industrial city of Kryvyi Rih in central Ukraine which damaged civilian infrastructure, homes and gas pipelines, the region's governor said.
