Russian forces are advancing in the northern Ukrainian region of Sumy, bringing the regional capital within range of their drones and artillery, according to Ukrainian officials and analysts.

Ukraine targeted at least four air bases across Russia using 117 unmanned aerial vehicles launched from containers close to the targets. Drone footage of the operation verified by Reuters shows several aircraft were struck in at least two locations.

A surprise Ukrainian drone attack that targeted Russian air bases hosting nuclear-capable strategic bombers was unprecedented in its scope and sophistication.