"Russian military medics are fighting to save their lives," the ministry said in a statement.
The vehicle was part of a motorcade transporting Syrian troops with the Russian military advisers from the Tiyas airbase to the city of Homs, when the mine detonated 2.5 miles away from the point of departure.
On June 16, Russian Sergeant Andrei Timoshenkov died in hospital a day after he had entered into a battle against suicide bombers while guarding a humanitarian aid distribution point in Homs province. The soldier opened fire on one of three vehicles filled with explosives and stopped it, receiving lethal injuries in an explosion.
Since 2011, Syria has been engulfed in a civil war, with government forces fighting against numerous opposition and terrorist groups, including al-Nusra Front and Daesh, banned in a range of countries, including Russia.
Moscow has been conducting a counter-terrorist campaign in Syria since September 30, 2015, at President Bashar Assad's request.