The attack on Friday, which killed at least four people nationwide, came two days after Russia vowed retaliation for an audacious drone assault on its strategic bomber bases.

A large Russian drone-and-missile attack targeted Ukraine's eastern city of Kharkiv on Saturday, killing at least three people and injuring 21, local officials said. The barrage — the latest in near daily widescale attacks — included aerial glide bombs that have become part of a fierce Russian onslaught in the three-year war.