Ukraine attacked Russia's Morozovsk military air base in the Rostov region, destroying six Russian warplanes in a joint operation conducted by the SBU security service and military, a Kyiv intelligence source told Reuters on Friday.

Reuters could not independently verify the claim. The source did not say how the attack was conducted but that eight more warplanes had also been damaged.

Russia's RIA news agency cited the Russian defence ministry earlier as saying Russian air defences had downed 53 Ukrainian drones overnight, most of them over the Rostov region.

The source said the Morozovsk air base was used by Russian tactical bombers like the Sukhoi Su-24 and Su-24M that Moscow's air force uses to fire guided bombs at the Ukrainian military and frontline towns and cities.

The source described the operation as an important one.

Ukraine has significantly stepped up its drone attacks on targets in Russia in recent weeks, focusing on oil refineries in an effort to reduce Russian oil revenue.

A senior government official told Reuters earlier this year that Ukraine hoped to produce thousands of long-range drones in 2024, part of a priority defence programme in its war with Russia.

Unable to rapidly produce long-range missiles and with limited access to those made by Western allies, Kyiv has focused on developing long-range uncrewed vehicles to strike back at Russia, which has used a sprawling arsenal of missiles and drones to bomb Ukraine. (Reporting by Tom Balmforth; Editing by Peter Graff and Nick Macfie)