Hours later, Russia launched a glide bomb and a drone at the front-line town of Kostyantynivka in eastern Ukraine, killing four civilians and injuring a fifth, the prosecutor’s office said. The drone struck a car in which a married couple were travelling, killing the 39-year-old woman and 40-year-old man on the spot, it said.

Ukraine said it struck a Russian air base on Saturday, while Russia continued to attack Ukraine with hundreds of drones overnight as part of a stepped-up bombing campaign that has dashed hopes for a breakthrough in efforts to end the more than 3-year-old war.

Ukraine has concluded deals with European partners and a US defence company to step up the production of drones, President Volodymyr Zelensky said on Saturday. Zelensky said Kiev has "reached an agreement with one of the leading American companies to significantly increase our joint efforts" on drones,