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

Kyiv, Ukraine — Russia bombarded six regions of Ukraine in one of its largest aerial attacks of the three-year war, Ukrainian officials said Friday. The nighttime assault lasted for hours and killed three emergency responders in the capital Kyiv, according to authorities.

Russia's Defence Ministry said on Friday that its forces had carried out a massive and successful strike on military and military-related targets in Ukraine overnight in response to what it called Ukrainian "terrorist acts" against Russia.