A nighttime missile and drone attack on Ukraine killed at least four people and injured 20 others in Kyiv, city mayor Vitali Klitschko said Friday, as Russia targeted at least six regions across the country with 407 drones and 44 missiles in one of its largest co-ordinated attacks of the three-year war.

Russia launched a drone and missile attack on Ukraine's capital and other parts of the country on Friday, officials say.

Operation of the city's metro transport system was disrupted because a Russian strike had hit and damaged a train between stations. The air attack also triggered fires in residential buildings.