The soldier, named as Anton Yerygin, "sustained serious injuries after coming under fire by rebels while escorting vehicles of the Russian coordination centre mediating between the warring sides", the unnamed official told Interfax news agency.
Yergyin died after doctors fought for his life for two days at the military hospital where he was taken shortly after the assault, the official added.
He did not specify however when the assault had taken place, or when exactly the soldier died.
The death came after the body of a Russian special forces officer killed in late March close to Palmyra was flown back to his home town on May 5 in a full military ceremony.
Russia said on Tuesday it had delivered bread to parts of Homs province and extended the ceasefire to one more area of the battered region.
The announcement of the latest casualty also came hours before the expiry at midnight today of a Russian and US-brokered ceasefire in Aleppo.
Regime forces and rebels in the battleground city have already agreed to extend the truce twice.
