Russia launched a large-scale attack on the Ukrainian capital Kiev with drones and ballistic missiles, according to warnings issued by Ukraine's Air Force on Telegram.
The military also warned of a possible Russian attack with the new Oreshnik medium-range missile.
The Kyiv Independent reported a "series of explosions" in the capital early on Sunday. Eyewitnesses on social media also reported hearing blasts.
The full scale of the Russian attack and its consequences were not immediately clear.
Ukrainian President Volodymyr Zelensky had warned on Saturday evening that an Oreshnik attack was expected. Citing intelligence information, he said Kiev was also at risk.
Zelensky warned of a possible combined Russian attack involving different types of weapons and urged people to seek shelter during air raid alerts.
It initially remained unclear whether Russia had actually used an Oreshnik medium-range missile in the overnight attack on Kiev.
Russia has used the ballistic missile, which has a particularly high destructive power, twice before in its war against Ukraine - once without warheads in the south-eastern city of Dnipro and most recently in western Ukraine in January.
