On Sunday afternoon, almost 1,000 militants and their family members who have left their last strongholds in Eastern Ghouta arrived in the town of Qalat al-Madiq in Hama province, the Syrian news agency SANA reported.
Earlier on Monday, the group, the last in control of territory in eastern Ghouta, said on Sunday it would not withdraw to other opposition-held parts of Syria as other rebel groups have done under deals negotiated with Syrian government ally Russian Federation.
The Army of Islam has held Douma, near Damascus, for years.
Meanwhile, the Syrian Observatory for Human Rights placed the number of civilians leaving Eastern Ghouta at 140,000.
Syria's pro-government Al-Watan daily said the Army of Islam and the Russians have reached an "understanding", adding that each side will study a draft agreement within the next three days.
Douma is the only town on the eastern outskirts of the Syrian capital still held by rebels
A civilian committee representing Douma said in a statement released late Sunday after meeting Russian officials that the negotiations "are extremely hard and no quick results should be expected". Only the town of Douma has yet to surrender.
Four major rebel groups are now positioned inside Eastern Ghouta, namely the Islam Army, Failaq al-Rahman, Ahrar al-Sham, and the Levant Liberation Committee, known as the al-Qaida-linked Nusra Front.
Al Jazeera's Zeina Khodr reports from neighbouring Lebanon.
The Russian Defense Ministry's Center for Reconciliation in Syria said in a statement that more than 400 people left Douma early Monday.
The group has accused Syrian government of trying to change demographic balance of eastern Ghouta by forcing out locals and replacing them with its allies.
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