Russia fired hundreds of drones at Ukraine between late Thursday and early Friday, killing seven people and destroying a factory that produces milk products for children, authorities said.
Images published by Ukraine's state emergency service showed the ruins of a building bearing the logo of Ukrainian dairy producer "Yagotynske for Kids", its facade partly destroyed and flames visible on one floor.
"The enemy attacked a peaceful civilian food industry enterprise," Kyiv region governor Mykola Kalashnyk said in a post on Telegram.
"Unfortunately, the number of people killed as a result of the hostile attack... has increased to four people," AFP quoted him as saying in a later post.
Separate strikes on Ukraine's central Dnipropetrovsk region killed two people, regional governor Oleksandr Ganzha said, while a drone strike in the southern Zaporizhzhia region killed one woman, according to the Ukrainian state emergency service.
Russia fired at least 216 drones at Ukraine between late Thursday and early Friday, as well as two missiles, according to the Ukrainian air force.
Moscow and Kyiv have intensified drone strikes on each other in recent months as US-led diplomatic efforts to end the war, now in its fifth year, remain stalled over the conflict in the Middle East.
Ukrainian President Volodymyr Zelensky proposed a meeting with Vladimir Putin in an open letter to the Russian leader late Thursday, saying it was only the leaders who could resolve "key issues".
The Kremlin said it was aware of the letter but that Putin was yet to review it.
The Russian leader has previously ruled out meeting Zelensky before a final deal is agreed and has questioned his legitimacy.
Russia is demanding Ukraine fully withdraw from the eastern Donbas region as a precondition of any deal.
Ukraine wants a full ceasefire along the current front lines, pending negotiations on a territorial settlement.
