DAMASCUS, Nov. 1 (Xinhua) -- The ultra-radical rebel groups attacked positions of the Syrian government forces in the demilitarized zone at dawn on Thursday, marking the first attack on Syrian forces in the buffer zone, a war monitor reported.

A rebel group allied with the Hayat Tahrir al-Sham, umbrella group of the al-Qaida-linked Nusra Front, attacked the Syrian positions in the eastern countryside of Idlib Province in northwestern Syria, said the Syrian Observatory for Human Rights.

It was the first rebel attack on Syrian government forces since the demilitarized zone deal went into force last month.

The establishment of a demilitarized zone was the result of a Turkish-Russian agreement reached in September to separate the Syrian forces from the rebels.

According to the deal, the ultra-radical groups, mostly affiliated with al-Qaida, should withdraw their fighters and weapons from the zone, which forms a ring around Idlib, the last major rebel bastion in Syria.

However, the deal was only partially implemented, as the rebel fighters are yet to pull out despite the withdrawal of their heavy weapons.

The Syrian government said the deal to establish a buffer zone in Idlib should end with the province returning to the government control.

Syrian Foreign Minister Walid al-Moallem recently said terror groups are still present in Idlib, indicating that the Turkish side is not committed to the demilitarized zone deal.