The Kursk airbase in western Russia was damaged in a Ukrainian attack over the weekend, according to a report.
Counter-intelligence agents from Ukraine's Security Service (SBU) were involved in the attack on the night of 26-27 August, sources told The New Voice of Ukraine.
Attack drones hit four Russian Su-30 fighters, a MiG-29 aircraft, two Pantsyr air defence systems and S-300 radars, the source said.
The explosions were "very spectacular", they were quoted as saying, and the "precise results of the strikes and the number of casualties and wounded will be known soon".
Several powerful explosions were heard in Kursk that night.
The Russian defence ministry claimed it had successfully intercepted the drones - but the Ukrainian sources say otherwise.
