Two residential buildings in central Kyiv were hit during a Russian missile strike on the Ukrainian capital on Tuesday, city mayor Vitali Klitschko said.
He wrote on the Telegram messaging app that rescue workers were on the scene and that several missiles had also been shot down but gave no details of any casualties.
Footage posted on social media by the deputy head of Ukrainian President Volodymyr Zelensky's office showed flames pouring out of a small apartment block.
A Reuters correspondent who arrived on the scene after the attack said about 15 devastated residents had gathered around the smouldering side of the five-storey apartment block.
Officials warned residents to stay in shelter for fear of more attacks.
The missile strike on Kyiv followed air raid warnings across Ukraine hours after Zelensky delivered a video address to leaders of the Group of 20 nations who are meeting in Bali.
"Russia responds to @Zelensky's powerful speech at #G20 with a new missile attack. Does anyone seriously think that the Kremlin really wants peace? It wants obedience. But at the end of the day, terrorists always lose," Andriy Yermak, chief of the presidential staff, wrote on Twitter.
Russia has stepped up missile strikes on Ukraine in recent weeks, with missiles damaging energy infrastructure as well as residential buildings.