The Syrian Observatory for Human Rights said on Sunday that the Failaq al-Sham group has started withdrawing its forces and heavy arms from a demilitarized zone in northwest Syria.
The group is the first to comply with a requirement to leave a demilitarized buffer zone set up by Turkey and Russia to avert a Russian-backed Syrian army offensive, Rami Abdulrahman, head of the UK-based war monitor told Reuters.
"The group is withdrawing its forces and heavy arms in small batches from southern Aleppo countryside, adjacent to Idlib province, which is part of the DMZ towards the west," Abdulrahman said.
The demilitarized zone will be 15 to 20 kilometers (10 to 12 miles) deep, run along the contact line between opposition and government fighters, and will be patrolled by Turkish and Russian forces.
Turkey and Russia had agreed in mid-September to enforce a new demilitarized zone in Idlib province from which radical groups will be required to withdraw by the middle of next month.
Failaq al-Sham is the third largest armed group in Northwest Syria, according to the monitor.