Ukraine has carried out large-scale drone strikes against four airbases deep inside Russia, destroying multiple combat planes, according to a source in the Ukrainian Security Service (SBU).

Russia’s Defense Ministry said on Sunday that Ukrainian drones attacked airfields in five regions, and that several aircraft had caught fire.

Ukraine destroyed Russian strategic bombers in a mass drone attack on airfields across Russia, sources have claimed. The operation, carried out by Ukraine’s security service, appears to have targeted at least two airfields thousands of miles from the frontline.