Pro-Ankara rebels began withdrawing from areas in northern Syria on Sunday, a monitor said, under a Russian-Turkish deal to avert a massive assault on the country's last major opposition stronghold.
Reached earlier this month between regime ally Moscow and rebel backer Turkey, the accord provides for a buffer zone around the northern region of Idlib that would be free of jihadists and heavy weapons.
Sunday's reported pullout of fighters and their heavy arms from areas near Idlib is the first indication that the landmark deal is being implemented.
The Syrian Observatory for Human Rights said the Faylaq al-Sham rebel group began leaving parts of the neighbouring province of Aleppo on Sunday "with heavy weapons, including tanks and cannons".
Faylaq al-Sham has some 8,500 to 10,000 fighters who are part of a Turkish-backed alliance known as the National Liberation Front (NLF).
The NLF, according to Abdel Rahman, is "the second most powerful group in northern Syria in terms of military equipment and the third largest in terms of manpower".
It cautiously accepted the Idlib agreement just over a week ago, pledging "full cooperation" with Turkey.
There was no immediate comment from Faylaq al-Rahman on Sunday's withdrawals, and it was unclear whether other NLF factions were preparing to do the same.
- Jihadists, rebels split on deal -
On September 17, Russian President Vladimir Putin and Turkish counterpart Recep Tayyip Erdogan agreed to set up a demilitarised zone about 15 to 20 kilometres wide ringing around Idlib.
All factions in the planned buffer must hand over their heavy weapons by October 10, and radical groups must withdraw by October 15, according to the agreement.
The deal was welcomed by world powers, aid organisations, and the United Nations, which all hoped it would help avoid a bloody military assault on the area.
But observers have pointed out its implementation would be tricky for Ankara.
Most of the territory where the zone would be established is controlled by either hardline jihadists or by Hayat Tahrir al-Sham, which is led by former members of Al-Qaeda's Syria branch and widely considered the most powerful force in Idlib.
The rest is held by the NLF and other rebels.
HTS has yet to announce its position on the agreement, and there have been no signs it was moving out either fighters or heavy weapons.
But Al-Qaeda loyalists Hurras al-Deen, which have a presence in the zone, rejected the deal last week.
And on Saturday, formerly US-backed rebel group Jaish al-Izza followed suit.
"We are against this deal, which eats into liberated (rebel-held) areas and bails out Bashar al-Assad," its head Jamil al-Saleh told AFP.
Jaish al-Izza, which is not part of the NLF, clashed with regime forces throughout the night on Saturday and into Sunday in the province of Hama, bordering Idlib.
- 'Purge' fighters -
Separate clashes were also taking place in the coastal province of Latakia between jihadists and government fighters, said the Observatory on Sunday.
Idlib and adjacent rebel territory are home to some three million people, about half of them displaced from other parts of Syria.
Seven years of brutal war have forced more than half of Syria's people out of their homes, sending more than five million into neighbouring countries to seek refuge and leaving another six million internally displaced.
After losing swathes of territory to rebel fighters, Syrian President Bashar al-Assad appears to have regained the upper hand and now controls around two-thirds of the country.
The areas still escaping his control are Idlib in the northwest, and a northeastern chunk held by Kurdish authorities where US and other Western troops are present.
On Saturday, Syrian Foreign Minister Walid Muallem addressed the United Nations General Assembly in New York, saying Damascus would keep "fighting this sacred battle until we purge all Syrian territories" of both terror groups and "any illegal foreign presence".