More than 40 Russian military aircraft have been destroyed in a large-scale drone attack, a Ukrainian official has said.Tu-95 and Tu-22 strategic bombers, which Russia uses to fire long-range missiles at Ukraine, were among the planes struck by Ukraine's domestic security agency, the SBU, an SBU source told Reuters. The report could not be independently verified.Pro-Russian bloggers said Ukraine attacked Russian nuclear-capable long-range bombers at a military base in Siberia on Sunday.Unverified video and pictures posted on social media showed Russian strategic bombers on fire at the Belaya air base north of Irkutsk.