Two officers and three crew were on board a Russian military helicopter shot down on August 1 in the northwestern province of Idlib, which is almost entirely under the control of a coalition of opposition groups.
The Syrian regime has started releasing 169 captives, including women, in exchange for the bodies of five Russian airmen who were killed when their helicopter was shot down by opposition groups, a lawyer representing the prisoners said on Wednesday.
The attack was one of the deadliest for Moscow since it intervened in the conflict in September 2015 in support of Syrian regime leader Bashar al-Assad, taking the overall number of Russian soldiers killed in the country to 18.
"On Tuesday, 50 inmates including seven women were set free from Adra prison and 84 others from Hama prison," Michel Chammas, a lawyer who represents the prisoners said.
Another 31 inmates at Homs prison and four others held elsewhere were also informed that they would be released.
Two officers and three crew were on board a Russian military helicopter that was shot down on August 1 in the northwestern province of Idlib, which is almost entirely under the control of a coalition of opposition forces.
Chammas declined to say which opposition groups were involved in the negotiations with the regime.
The Syrian Observatory for Human Rights, a monitoring group, said 86 people had been released in the central city of Hama.
Earlier in July, two Russian pilots were killed in Syria after DAESH shot down a Syrian Mi-25 helicopter near Palmyra.
Over five years of war in Syria has failed to break the deadlock between the regime and rebels groups, despite numerous attempts to implement ceasefires and establish dialogue.
According to some estimates, as many as 470,000 people may have died in the war.
As much as half of Syria's population has been displaced, triggering the worst refugee crisis the world has seen since World War II.