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.

Russia launched an intense missile and drone barrage at the Ukrainian capital Kyiv in the early hours of Friday, killing at least six people, Ukrainian officials said, as powerful explosions reverberated across the country.

Officials say Ukraine was under an ongoing Russian ballistic missile and drone attack early Friday that wounded at least three people.