Russia's defense ministry said Thursday that a military adviser with the rank of major had been killed in an attack in Syria, Interfax news agency reported.
Major Sergei Bordov was killed in after a rebel attack on a military base of government forces, the ministry said.
"The serviceman was in a group of Russian military advisers carrying out tasks to train a unit of Syrian forces," the defence ministry said.
"During an attack by rebels, the Russian officer organised the actions of Syrian troops, not allowing the terrorists to break through into a residential area," the ministry said, adding that he had been nominated for a posthumous award.
"During the battle the officer suffered fatal wounds."
The death brought the toll of soldiers killed in combat in Syria officially acknowledged by the defence ministry to 30. Another soldier committed suicide during the first month of the operation.
In the previous fatal incident announced this month, two servicemen acting as military instructors to a unit of troops loyal to the Assad regime were killed in a mortar attack.