At least three children were among 27 people wounded as a result of a Russian drone attack on Ukraine's second-largest city of Kharkiv overnight that damaged apartments and a kindergarten, Ukrainian authorities said on Monday.

Russia launched 550 drones and missiles across Ukraine overnight in the largest aerial assault since the war began. The capital Kyiv was the primary target.

Russia and Ukraine struck each other with hundreds of drones on Sunday, throwing Russian air travel in disarray, shortly after Ukrainian President Volodymyr Zelenskyy announced deals with Western partners that would allow Kyiv to scale up drone production.