The group in control of the last rebel bastion near Damascus appear to have agreed a deal for its fighters to make peace with the government or quit Syria's eastern Ghouta enclave, state media says.
Jaish al Islam, most of whose members are drawn from the area, has been defending the city of Douma against a months-long onslaught by government forces.
If confirmed, its surrender or departure for rebel-held areas in northwest Syria would herald an end to large-scale conflict in the enclave.
State television and Syrian newspapers said information indicated that, under the deal, the group would hand over heavy and mid-sized weapons and acknowledge the restoration of state sovereignty over Douma.
Jaish al Islam had no immediate comment on the reports.
The government lost control of Douma, the largest urban centre in the eastern suburbs of Damascus remaining in insurgent hands, in the early phase of Syria's civil war, which is in its eighth year.
If confirmed, the agreement with Jaish al Islam would mirror others reached by insurgents following heavy bombing of areas under their control by government forces and Russian jets that has led to hundreds of casualties among civilians.
Late on Saturday, negotiators reached a deal to evacuate wounded Jaish al Islam civilians and fighters to Idlib in the northwest.
A group of stranded fighters from another insurgent group, Failaq al Rahman, left Douma on Sunday, state media said.
On Saturday it concluded a week-long evacuation of thousands of its fighters from areas it had controlled in other parts of the enclave.
