The Syrian army has made a significant advance in its effort to take rebel-held Eastern Ghouta, reports say.
Troops have cut off the region's biggest town, Douma, and isolated another, according to UK-based conflict monitors the Syrian Observatory for Human Rights (SOHR).
The advance would effectively split the region into three parts.
The Syrian government began a major offensive last month to re-take Eastern Ghouta, near the capital Damascus.
Since then they have reportedly taken control of half of the region, in an advance that has left around 1,000 civilians dead over the past three weeks, according to SOHR.
The UN has called the bombardment "unacceptable", saying it amounts to "the collective punishment of civilians".
The military has been accused of targeting civilians, but it says it is trying to liberate the region - one of the last rebel strongholds - from those it terms terrorists.
A clear strategy of the Syrian government's offensive in Eastern Ghouta has been to divide the enclave into isolated sections and so cut off rebel support and supply networks.
The Syrian government has reportedly captured the central town of Misraba, and advanced onwards into surrounding farmland.
Misraba is located along a major road that links Douma, in the north, with another big town, Harasta, in the west.
If confirmed, the advance leaves the enclave divided into three - Douma and its surrounding towns in the north, western Harasta, and the rest of the territory in the south.
Some 400,000 people are still thought to live in the area, seven years into Syria's civil war. It has been besieged by government forces since 2013.
Who are the rebels?
The rebels in Eastern Ghouta are not one cohesive group. They encompass multiple factions, including jihadists, and in-fighting between them has led to past losses of ground to the Syrian government.
The two largest groups are Jaish al-Islam and its rival Faylaq al-Rahman. The latter has in the past fought alongside HTS.
Eastern Ghouta is so close to Damascus that it is possible for rebels to fire mortars into the heart of the capital, which has led to scores of civilian deaths.
The Syrian government is desperate to regain the territory, and has said its attempts to recapture it can be attributed directly due to the HTS presence there. HTS was excluded from a ceasefire agreed at the UN that has yet to come into effect.
The group is an alliance of factions led by the Nusra Front, which sprang from al-Qaeda.