The Russian military says four of its servicemen were killed in Syria when their vehicle struck a roadside bomb.



The Defense Ministry says the explosion happened as a Syrian military convoy, including the vehicle with Russian military advisers, was driving to the city of Homs in central Syria last Thursday from the Tiyas air base, which is close to the ancient town of Palmyra held by the Islamic State group.



The ministry says the bomb was detonated by remote control. Two other Russian servicemen were wounded.



The deaths bring the number of Russian combat casualties in Syria to 27.



No group has claimed responsibility for the attack.



Russia launched its military operation in support of Syrian President Bashar Assad's forces in September 2015, helping his troops regain some key ground.