Security sources tell BBC Ukrainian another eight bombers were badly damaged in the attack.

Ukraine has carried out a drone attack against targets in southern Russia, and claims to have destroyed six Russian planes at an airbase in Rostov region.

Security sources told BBC Ukrainian eight more aircraft were badly damaged, and 20 service personnel could have been killed or injured.

The Morozovsk base houses Su-24, Su-24M and Su-34 aircraft used on the front line in Ukraine, the sources said.

There has been no word from Russia on reports of an airfield attack.