More than 1,500 rebels and their family members left the devastated district of Qaboun on the edge of Damascus on Sunday, as the Syrian army and its allies continue to advance in areas in and around the capital, rebels and state media said.

Hundreds of rebels and their families were evacuated this week from the adjacent Barzeh district after rebels there decided to lay down their arms and leave to rebel-held Idlib province.

Syrian state media said evacuations had almost been completed and the district was now securely in army hands.

The evacuation will see rebels and civilians move to Idlib, an opposition stronghold in northwestern Syria.

The loss of Qaboun so soon after Barzeh is another blow to rebels as they battle to keep a foothold in the capital and face government troops who are supported by Russian air power and Iranian-backed militias.

The UK-based Syrian Observatory for Human Rights estimated that government forces have taken back most of the neighbourhood, leaving around 20 percent still under the control of rebel groups Ahrar al-Sham, Jaysh al-Islam and the Rahman Corps.

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Syrian President Bashar al-Assad has promoted the use of such evacuations, along with what his government calls "reconciliation" deals for rebel-held areas that surrender to the government, as a way of reducing bloodshed in the six-year-old civil war.

Siege tactics

However, the United Nations has criticised both the use of siege tactics, which precede such deals, and the evacuations themselves as amounting to forcible displacement.

The Syrian army has been steadily defeating pockets of rebellion near the capital, with the help of Russian air power and Iranian-backed armed groups.

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The army offensive entered a higher gear in recent months in Barzeh and Qaboun, ending a local truce that had been in place with rebels there since 2014 and shutting access to a network of underground tunnels which supplied besieged eastern Ghouta, causing supplies to dwindle and prices to rocket.

Similar evacuation deals in the Palestinian refugee camp of Yarmouk, also situated in southern Damascus, have fallen through time and again.

The Syrian conflict started as an uprising against Assad in March 2011, but quickly morphed into a full-scale civil war that has killed hundreds of thousands and displaced millions.