The Russian Defence Ministry said on Thursday it had started changing the make-up of its strike force in Syria as part of a previously announced partial drawdown, Russian news agencies reported.
The ministry was cited as saying that the first six SU-24 bombers had already been withdrawn, but that four SU-25 ground attack aircraft had flown out to Russia's Hmeymim air base in Latakia province as part of a planned rotation.
It said further aircraft would be withdrawn along with military personnel stationed at the base.
Russian President Vladimir Putin announced a ceasefire in Syria in late December and said Russia would pull back some of its forces in Syria, where its military intervention has turned the tide in favour of President Bashar al-Assad.
The head of the Russian General Staff, Valery Gerasimov, said last week that a Russian naval force led by the Admiral Kuznetsov aircraft carrier had begun withdrawing from the east Mediterranean.