AMMAN (Reuters) - Hundreds of rebels left the last major besieged opposition enclave in Syria on Monday, with thousands more expected to follow, responding to months of pressure by a Russian-backed government offensive, the army, rebels and residents said.

A first convoy of buses with hundreds of rebels and their families, accompanied by Russian military police, departed from the city of Rastan, starting a week-long evacuation from towns and villages in an enclave between the cities of Homs and Hama.

Rebels representing several major Free Syrian Army (FSA) factions capitulated to a Russian-imposed deal after marathon talks with Russian generals on May 2 in Dar al Kabira town in the northern Homs countryside.

The deal forced them to hand in heavy weapons and gave those rebels not ready to make peace with the army the option of leaving with light arms to rebel-held areas in northern Syria.

Draft dodgers would have a six-month reprieve.

Russia exerted pressure by pounding the main towns of the enclave, where over 300,000 inhabitants live, in an escalation that killed and wounded dozens, rebels and residents said.

The Russians closed a border crossing near a key road to prevent civilians fleeing, to raise pressure on mainstream rebels to accept the terms, rebels and residents said.

Fears that Russia and its Syrian ally would unleash an even tougher push, on the scale that ended rebel control of Aleppo in 2016 and eastern Ghouta last month, prompted the capitulation to spare civilian lives, residents and civilian negotiators said.

“They left rebels with no option after bombing civilians and giving them no choice either to submit or obliterate their areas and make civilians pay the price,” said Abul Aziz al Barazi, one of the civilian opposition negotiators told Reuters.

BOMBING

The war has been going President Bashar al-Assad’s way since Russia intervened on his side in 2015. From holding less than a fifth of Syria in 2015, Assad has recovered to control the largest chunk of the country with Russian and Iranian help.

A major bombing campaign that began last February ended the last remaining pockets of opposition resistance in the eastern Ghouta, the biggest enclave around the capital, that had for years withstood a siege and successive army onslaughts.

The fall of the once heavily defended Ghouta demoralized rebels in others areas further east of the capital closer to the Iraqi border and in a southern Damascus pocket.

Now the only besieged area left is a small enclave in southern Damascus, where a few hundred Islamic State militants are making a last stand as aerial strikes devastate the once teeming major Palestinian camp of Yarmouk, Syria’s largest, and nearby Hajar al Aswad town.

The last batch of rebels in the remaining south Damascus pockets, which includes the towns of Babila, Yalda and Beit Sahem, are expected to leave in the course of this week.

The Homs and Hama rebel enclave deal leaves the mainly Sunni civilians unprotected, leaving many residents there afraid of revenge by militias from surrounding Alawite villages.

Accordingly rebels in the enclave say that under the agreement they have gained assurances that the Russian military police would spread out and man checkpoints around the enclave for a renewable six-month period. The rebels see the move as a guarantee against the entry of paramilitary pro-Assad militias.

While Syria’s conflict is in part a proxy struggle among great powers, it is also has a sectarian element pitting the mainly Sunni-led rebels against the minority Alawite community to which Assad’s family belongs.

In the latest deal and in other areas, many have opted to stay and make peace with the army rather than leave their homes for an uncertain future in refugee camps in northern Syria.

The opposition accuse the authorities of pushing demographic changes that uproot Sunnis. The authorities deny this and say many civilians were held hostage by forces they call terrorists.