The glide bombs struck residential buildings in the south-eastern city on Saturday morning. Acting Mayor Regina Kharchenko told Ukrainian television from the scene that the ground floor of one apartment block was hit and the floors above collapsed. Search and rescue operations involving more than 80 workers were ongoing, with rescuers periodically stopping to listen for sounds from survivors under the debris.
President Zelensky said 13 other regions had also been hit overnight. He added: "Our responses to [these] Russian strikes will come."
Photos and videos from the site showed an apartment block mostly destroyed. Kharchenko described the attack as striking "our very heart" and said children were among the dead, calling their deaths "awful grief for their families. For the city."
The attack occurred just hours after US President Donald Trump announced a deal to import Russian diesel into the United States. Zelensky has heavily criticised the deal.