The mass grave contained 112 bodies that were executed by members of foreign-sponsored terrorist groups, Press TV reported.
Syrian Forensic Medicine General Director Zaher Hajo said on Thursday that the victims had most likely been killed during the heavy fighting in the former militant stronghold nearly two weeks ago.
The bodies have been sent to the forensic department to undergo an identification process.
Militants from the Jaysh al-Islam armed group and their family members have started to leave the city of Dumayr, located north-east of the Syrian capital of Damascus, local media reported Thursday.
Overall, 5,000 people, 1,500 of whom have families, were leaving Dumayr in five buses bound for Jarabulus in northern Syria, the country’s state TV said.
On Tuesday, the militants began surrendering their weapons as part of the agreement reached with the government forces.
Syria has been struggling to put an end to a civil war since 2011, with terrorist groups taking part in the conflict. At Damascus' request, Moscow has assisted in defeating Daesh, the most dangerous extremist formation and has been assisting in reinstating peaceful life in the country.
The Russian side has played a key role in organizing humanitarian corridors in Eastern Ghouta, providing civilians — as well as militants – with the opportunity to leave the area.