The pullback is in line with a plan agreed this month between regime ally Russian Federation and rebel backer Turkey to avert a large-scale government offensive on Idlib province and surrounding rebel territory, which included setting up a demilitarised zone.
The deal averted Idlib a wide-scale military offensive by the Syrian army, which expressed divisiveness in dealing with Idlib as it's the last major rebel stronghold in Syria.
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), Rami Abdurrahman, head of the UK-based Syrian Observatory for Human Rights, told the AFP news agency on Sunday.
The watchdog group said the initial withdrawal comes by the group to please the Turkish side, which along with the Russians, have agreed to establish a demilitarized zone as of October 15 between the Syrian forces and the rebel groups. "This report is denied, completely denied", NLF spokesperson Naji Mustafa told AFP.More news: NL Central champion Brewers to begin postseason play on October 4
It remains to be seen whether or not any rebel force will leave the buffer zone, as their failure to do so could result in a military operation by the Syrian military.
The Observatory said only Failaq al-Sham, deemed as the third most powerful rebel group in northern Syria, took the initiative to start withdrawing from Aleppo countryside.
The NLF was formed in August and merged the armed groups Ahrar al-Sham and Nureddine al-Zinki with other rebel factions with Turkey's backing.
Under the deal between Ankara and President Bashar al-Assad's key ally Moscow, the zone will run along the contact line between insurgents and government forces, and will be patrolled by Turkish and Russian forces.
The biggest jihadist group, Tahrir al-Sham, has yet to announce its position regarding the agreement.More news: NY Times: Trump Dubious Tax Schemes Pumped Up Fortune
But Al Qaeda loyalists Hurras Al Deen, which have a presence in the zone, rejected the deal last week.
The areas still outside his control are Idlib in the north-west, and a north-eastern chunk held by Kurdish authorities where United States and other western troops are present.
A formerly US-backed Syrian rebel group on Saturday rejected a deal between Russian Federation and Turkey to avert a large-scale military assault on rebel-held Idlib province.
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 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.More news: Pentagon Cancels Talks With China Amid Rising Tensions
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