The last Syrian rebel group in Eastern Ghouta near Damascus has begun withdrawing under an agreement with the government, Syrian state media has said.

However, one military source said a group of insurgents were still rejecting the deal.

The rebel group which has been defending the Eastern Ghouta town of Douma against a ferocious onslaught by Russian-backed Syrian government forces, has not confirmed the agreement with the government.

If confirmed, their departure from Douma would mark the end of the war for Eastern Ghouta, wiping out an opposition stronghold near Damascus and underlining President Bashar al-Assad's unassailable position in the war.

It will mark his biggest victory over rebels fighting to unseat him since the recovery of eastern Aleppo in 2016.

Syrian state TV said eight buses carrying 448 people - fighters and their families - had left Douma so far today, en route for the north.

State media has said the rebels are due to go to areas near the Turkish-Syrian border that are controlled by opposition groups.

The Syrian Observatory for Human Rights, which monitors the war, said dozens of buses had entered Douma early today in readiness to evacuate the rebels and their families to the northern towns of Jarablus and al-Bab, near the Turkish border.

The towns are located in a section of the Turkish-Syrian frontier where Turkey has carved out a buffer zone controlled on the ground by its military and allied fighters from Free Syrian Army rebel groups that are hostile to Assad.

Under the deal, Syrian state media said the rebels would hand over heavy and medium-sized weapons and acknowledge the restoration of the Damascus government's control of Douma.

The government lost control of Douma, the largest urban centre in the eastern suburbs of Damascus, in the early phase of Syria's civil war, now in its eighth year.

Buses have been evacuating fighters and their families since this morning

Thousands of rebels, their families and other civilians have already departed other parts of Eastern Ghouta for Idlib province, another insurgent-held area of northern Syria.

Tens of thousands more people have fled to shelters in government-held territory near Ghouta.

The government offensive on Ghouta has been one of the deadliest of the war, killing more than 1,600 civilians, according to the Observatory.

The government says it is restoring security to Damascus, which was regularly shelled from Eastern Ghouta during the war.

President Assad, who has military support from Iran and Russia, now controls the bulk of Syria, though it may be difficult for him to recover much more territory without risking a collision with other foreign powers that have forces inside the country.

The second largest chunk of Syrian territory is controlled by the Syrian Democratic Forces, an alliance of militias spearheaded by the Syrian-Kurdish YPG and supported by the US-led coalition against Islamic State.

US President Donald Trump added fresh uncertainty to the outlook for the conflict last week by indicating that the United States would soon be leaving Syria.

Mr Trump has told advisers he wants an early exit of US troops from Syria, two senior administration officials said on Friday, a stance that may put him at odds with US military officials who see the fight against Islamic State as nowhere near complete.

Turkey, alarmed by the growth of Kurdish influence in Syria, has recently expanded its foothold in the north of the country by seizing the northwestern Afrin region from the YPG, supported by Turkey-backed Syrian militias.

Rebels also still control a significant chunk of territory on the frontiers with Jordan and Israel, which are both anxious about the growth of Iranian influence in Syria.