A concentrated, nine-minute-long Russian drone attack on Ukraine's second largest city of Kharkiv in the middle of the night killed at least two people and injured 57, including seven children, regional officials said on Wednesday.

The assault continued Moscow’s stepped-up drone and missile attacks, which have been ratcheting up for months with nightly bombardments on regions and cities in Ukraine.

Ukrainian officials say three people were killed and 13 were wounded when Russia attacked the country with waves of drones and missiles.