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.

After Russia launched a record missile and drone attack on Kyiv and other Ukrainian cities overnight on July 4, Ukraine responded the following night with drone strikes across multiple regions of Russia.

LONDON—Ukraine said it struck a Russian air base on Saturday, while Russia continued to pound 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.