Russia's Defence Ministry announced late on Monday that it had killed "up to 200 militants" in Syria during an airstrike on "terrorist facilities" northeast of Palmyra, Russia's Interfax news agency reported.
"After confirming data through multiple channels on the location of terrorist facilities, Russian Aerospace Forces aircraft carried out airstrikes," Rear Admiral Alexander Karpov, the head of the Russian military's Reconciliation Centre in Syria, said in a statement.
"Two hideouts were destroyed, up to 200 militants, 24 pickup trucks with large-calibre machine guns, as well as about 500 kilogrammes of ammunition and components for creating improvised explosive devices," he added.
According to the Russian official, the camouflaged bases served as a staging area to plan attacks on Syrian government institutions in major cities to destabilise the country ahead of the presidential elections scheduled for 26 May.
Russia deployed air forces to the Hmeimim base in Syria in 2015 to support President Bashar Al-Assad's forces. Its intervention changed the balances of power in the war-torn country and allowed Al-Assad to regain large swathes of land he had lost to opposition forces.