Beirut: Pro-Turkey rebels began Sunday withdrawing from areas in northern Syria under a deal brokered by Ankara and Moscow to avert a large-scale military assault on the country’s last major opposition stronghold, a monitor said.

Fighters from the Faylaq Al Sham group “began pulling out of areas in the southern countryside of Aleppo and the western suburbs of Aleppo city with heavy weapons, including tanks and cannons,” said the Britain-based Syrian Observatory for Human Rights.

The pullback is in line with a plan agreed this month between regime ally Russia 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.

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), Observatory head Rami Abdul Rahman told AFP.

The NLF was formed in August and merged extremist groups Ahrar Al Sham and Nureddine Al Zinki with other rebel factions with Turkey’s backing.

It is aimed at countering the growing power of Hayat Tahrir Al Sham (HTS), led by Al Qaida’s former Syria’s affiliate, which controls 60 per cent of Idlib.

The NLF controls the rest of Idlib province but is also active in parts of neighbouring Aleppo, Hama and Latakia provinces.

“It is the second most powerful group in northern Syria in terms of military equipment and the third largest in terms of manpower,” Abdel Rahman said.

On September 17, Russian President Vladimir Putin and Turkish counterpart Recep Tayyip Erdogan agreed to set up the demilitarised zone after talks in the Russian resort of Sochi.

Under the agreement, a 15-20 kilometre wide corridor is to be established by October 15 from which all extremist fighters must withdraw, paving the way for Turkish and Russian patrols of the area.

This would entail a “withdrawal of all radical fighters” from Idlib, Putin said at the time.

Erdogan said the measures would “prevent a humanitarian crisis”.

Russia-backed Syrian regime forces have massed around Idlib province in recent weeks, sparking fears of an imminent air and ground attack to retake the opposition bastion.

The United Nations, which cautiously backed the Russia-Turkey deal, had warned that an all-out assault on Idlib would trigger a humanitarian catastrophe and possibly one of the worst bloodbaths of Syria’s seven-year war.