Coalition air strikes Saturday killed at least 36 civilians related to the Islamic State group in a jihadist holdout in eastern Syria near the Iraqi border, a Britain-based monitor said.

Jihadists on Friday killed nine Syrian regime fighters near a planned buffer zone around the country's last major rebel bastion, a monitor said.

Syrian President Bashar al-Assad has called on the country's Druze community to do military service, days after members of the minority were released following a mass abduction in July by the Islamic State group.

Syrian government forces killed 23 rebels near Idlib province on Friday, the deadliest clash to rock a buffer zone where a Russian-Turkish truce is to be enforced.

United Nations chief Antonio Guterres has informed the Security Council that he wishes to appoint Norwegian diplomat Geir Pedersen as the next special envoy to Syria, diplomatic sources told AFP Tuesday.

The UN Security Council will meet Friday to discuss Syria, diplomatic sources told AFP Thursday, as no progress appears to have been made with Damascus on establishing a post-war constitution.

Amnesty International on Monday condemned the US-led coalition's failure to acknowledge and investigate its role in civilian killings during the battle a year ago to oust jihadists from Syria's Raqa.

A deadline for jihadists to leave a planned buffer zone around Syria's last major rebel bastion of Idlib passed Monday without any sign they had done so, said the Syrian Observatory for Human Rights.

A planned buffer zone in northwest Syria has been cleared of heavy armaments ahead of time but a new deadline loomed Wednesday for the tougher task of Turkey convincing jihadists to pull out their fighters.

Jihadists and Turkish-backed rebels in Syria's last major opposition stronghold have withdrawn most of their heavy weapons from a planned buffer zone ahead of a Wednesday deadline, a monitor said.

The pullback is the first major test of a deal brokered by government ally Russia and rebel-backer Turkey last month to avoid what the United Nations warned would be the appalling humanitarian consequences of a major government offensive.