The Syrian army intensified its onslaught in eastern Ghouta yesterday with advances that a war monitor and state media said had splintered the enclave, though a rebel official denied this.

Syrian state television broadcast from inside the town of Mesraba, a town lying along the road connecting the northern and southern halves of the rebel-held enclave, after reporting that the army had taken it earlier yesterday.

The capture of Mesraba and advances into nearby farmland brought important roads directly under fire by the army, the Syrian Observatory for Human Rights said.

That has in effect cut the large towns of Harasta and Douma off from each other and the rest of the enclave, it added.

However Hamza Birqadar, a spokesman for Jaish al-Islam, one of the two main insurgent groups in eastern Ghouta, said rebels had repelled the attack on Mesraba and neither Harasta nor Douma were cut off.

The relentless three-week assault on the last major rebel stronghold near Damascus has captured about half its area and killed 976 people, according to the Britain-based Observatory.

Syrian President Bashar al-Assad and Russia, his main ally, say the campaign is needed to end rebel shelling of Damascus and to end the rule of Islamist insurgents over the area's civilians.

The offensive follows the pattern of previous assaults on rebel strongholds, deploying massive air power and tight sieges to force insurgents to accept "evacuation" deals.

These involve rebels surrendering territory in exchange for safe passage to opposition areas in northwest Syria, along with their families and other civilians who do not want to come back under Assad's rule.

Smoke billows following Syrian government bombardment on the rebel-controlled town of Misraba, in the eastern Ghouta region on the outskirts of the capital Damascus yesterday. Syrian regime forces cut off the largest town in Eastern Ghouta from the rest of the opposition enclave in a blow to beleaguered rebels defending their last bastion near Damascus. Photo: AFP

Late on Friday, a small number of fighters and their families from the former al-Qaeda affiliate previously known as the Nusra Front left eastern Ghouta under such a deal.

But the group represents only a small portion of the insurgent presence in the enclave, and both Jaish al-Islam and the other main eastern Ghouta rebel group Failaq al-Rahman have said they are not negotiating a similar deal for themselves.

Capturing the enclave would represent Assad's biggest blow against the rebels since they were driven from Aleppo in December 2016.

It would seal a string of military victories for the Syrian leader since the entry of Russian jets into the war on his side in 2015 turned the course of the conflict against the insurgents.