BEIRUT (Reuters) - Syrian rebels began to evacuate an enclave in southwestern Syria on Friday under a surrender deal with the government as the army thrust into the northwest -- the insurgents’ main remaining stronghold.

State television showed footage of the convoy of buses containing the rebels moving out of Beit Jin.

Government forces and allied Shi’ite Muslim militias have forced numerous rebel pockets to surrender since Russia brought in heavy air power to help them in 2015, pushing the insurgents into an ever smaller number of enclaves.

The northwestern area around Idlib province is the rebels’ most important territory. They also hold a large area bordering Jordan and the Israeli-controlled Golan Heights near Deraa in the southwest, as well as scattered pockets elsewhere including eastern Ghouta near Damascus.

The International Committee of the Red Cross and the Syrian Red Crescent said on Friday they had finished a medical evacuation of 29 very sick people from eastern Ghouta as part of a swap deal for prisoners held by the rebels.

Fighters and their families started to leave Beit Jin, 40 km (25 miles) southwest of Damascus, on Friday after losing nearby areas to the army and its allies in heavy fighting earlier this month, state television reported.

Some were heading to Idlib in the northwest, an area controlled by jihadists and the destination for all previous evacuees from surrendered rebel pockets, others to rebel territory in the southwest held by nationalist insurgents.

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Beit Jin’s location near Israeli-controlled territory made it a strategic flashpoint given the role of Lebanon’s Hezbollah group -- Israel’s sworn enemy -- in fighting the rebels there.

Israel has bombed Hezbollah convoys and weapons caches several times in Syria this year and fired on military positions in Syria after projectiles landed in the Golan Heights.

The Syrian army’s advance against rebels in the northwest involved bitter fighting and intense air strikes on Thursday and Friday, according to the Syrian Observatory for Human Rights, a war monitor.

Fighting killed dozens on Friday and is concentrated in the village of Abu Dali in southern Idlib after weeks of incremental government gains in adjacent areas of Hama province.

The army has only recently advanced into Idlib for the first time since a string of rebel victories there evicted the government from the province in early 2015.

The government’s gains across many fronts have ended rebel hopes of ousting President Bashar al-Assad by force.

On Friday his office distributed photographs of Assad meeting a family in Homs, a sign of his growing comfort traveling around Syria this year after years in which he mostly stayed in Damascus.