The regime's offensive on Ghouta has killed more than 1,500 civilians [Getty]

The second-largest rebel group in Syria's Eastern Ghouta have declared a ceasefire in order to negotiate leaving the opposition enclave, as rebels and their families begin to leave the area.

The second-largest rebel group in Syria's Eastern Ghouta have declared a ceasefire in order to negotiate leaving the opposition enclave, as rebels and their families begin to leave the area.

Failaq al-Rahman will abide by a ceasefire as of midnight on Thursday, Syrian pro-regime media and the Britain-based Syrian Observatory for Human Rights reported on Thursday.

A spokesman for the rebel group has confirmed the move.

Air raids have targeted the part of Ghouta under the control of the Failaq al-Rahman.

The announcement about the faction's plans came shortly after hundreds of Syrian opposition fighters from a hardline Islamist rebel group began evacuating a key besieged town in Eastern Ghouta.

The only group that remains in the enclave will be the powerful Army of Islam, when Failaq al-Rahman evacuates Eastern Ghouta.

Carrying their light arms, hundreds of defeated rebels began evacuating with their families on Thursday, an effective surrender under a deal with the regime after a long siege and bombing campaign.

The departure of the powerful Ahrar al-Sham group - the first such arrangement for eastern Ghouta - could serve as a blueprint for fighters in other towns, bringing President Bashar Assad's government closer to ending years of rebellion in the territory just east of the capital.

As night fell, Syrian state television showed dozens of white buses carrying opposition fighters and civilians pulling out in a long convoy after being parked all day on a main highway.

The deal will see 1,500 rebels and 6,000 civilians depart, according to the state-affiliated Military Media Center.

The air and ground assault, which escalated on February 18, has seen the once-sprawling territory at the edge of the capital shrink to three disconnected rebel-held islands.

Eastern Ghouta is home to more than 400,000 people living under crippling regime siege, with little access to food or medical resources.

World leaders and the United Nations have sharply criticised the Assad regime for its indiscriminate bombing and called for an immediate halt.

But airstrikes continued to pound Ghouta on Thursday, with monitors confirming at least 19 were killed as the Syrian regime pressed an offensive on the Damascus suburb.

The regime's offensive on Ghouta has killed more than 1,500 civilians since February 18