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

Ukraine unleashed more than a hundred drones smuggled deep into Russia in what it called its most damaging attack yet.

Russia’s Defense Ministry in a statement confirmed the attacks, saying they damaged aircraft and sparked fires on air bases in the Irkutsk region, as well as the Murmansk region in the north. It said strikes were also repelled in the Amur region in Russia’s Far East and in the western regions of Ivanovo and Ryazan, the ministry said.