France and Russia on Saturday despatched a plane carrying humanitarian aid to the ravaged former Syrian rebel enclave of Eastern Ghouta, which was retaken by government forces in April after a five-year siege.

The Syrian army bombarded jihadists in the last area outside government control near Damascus on Friday, as President Bashar al-Assad accelerated his push to retake remaining enclaves.

Syrian regime forces shelled the last pockets in Damascus controlled by the Islamic State group, preparing the ground for a possible assault on the jihadist stronghold, a monitor said Wednesday.

The Syrian army has declared that all anti-regime forces have left Eastern Ghouta, after a blistering two month offensive on the rebel enclave on the outskirts of the capital.

International chemical weapons experts were travelling to Syria to investigate an alleged gas attack by government forces on Douma which killed dozens of people.

President Bashar al-Assad's government has invited international inspectors to send a team to Syria to investigate an alleged chemical attack in the town of Douma in a move apparently aimed at averting possible Western military action over the incident.

Qatar has strongly condemned the use of chemical weapons by the Syrian regime in the town of Douma in Eastern Ghouta, calling for an urgent international investigation and bringing war criminals in Syria to international justice.

Iran on Sunday condemned allegations of a chemical attack on Syria's Eastern Ghouta rebel holdout as a "conspiracy" against its ally President Bashar al-Assad and a pretext for military action.

Qatar Charity (QC) has distributed blankets to 23,000 internally displaced persons (IDPs) of Eastern Ghouta to alleviate their suffering, especially in the bitter winter.

Deadly air strikes slammed into the last opposition-held town in Syria's Eastern Ghouta on Friday for the first time in over a week, after talks sputtered over a rebel withdrawal.

Air strikes on the last rebel-held town in Syria's Eastern Ghouta killed 27 civilians on Friday, a monitor said, after talks sputtered over a deal for the battered town.

The UN humanitarian adviser for Syria called on Wednesday for access to the eastern Ghouta town of Douma, where he said some 80,000-150,000 civilians were "on their knees" after years of siege and fighting.