Satellite photos analyzed by The Associated Press on Wednesday show seven destroyed bombers on the tarmac at a Russian air base in eastern Siberia, one of the targets Ukraine said it struck with drones in one of the most daring covert operations of the war.

The photos provided by Planet Labs PBC show aircraft wreckage and scorched areas at the Belaya Air Base, a major installation for Russia’s long-range bomber force. In the images, at least three Tu-95 bombers and four Tu-22Ms appear to be destroyed. The planes were parked on an apron beside a runway surrounded by grassland. Other aircraft at the base appear unscathed.

Ukraine said that 41 Russian warplanes, including strategic bombers and other types of combat aircraft, were destroyed or damaged in Sunday’s operation, which officials said was planned over 18 months. The attack delivered a heavy blow to Russia’s air force and its military prestige.

It has so far been impossible to confirm the full extent of the damage. Russia has claimed Ukraine’s estimates are exaggerated.