Syrian government forces have split a rebel-held enclave in three parts, in a significant step toward retaking the area outside the capital, Damascus.
The Syrian Observatory for Human Rights, a British-based monitoring group, said government forces cut off Douma, the biggest town in eastern Ghouta, and isolated another.
The advance has effectively split the region into three parts.
Syrian government forces launched an offensive to take control of eastern Ghouta in February, in an advance that has left more than 1,000 civilians dead, according to the observatory.
The United Nations has called the bombardment "unacceptable," saying it amounts to "the collective punishment of civilians."
The monitoring group said at least 20 civilians were killed in Douma on March 10, in addition to 17 civilians in other battlefront towns.
The group said the deaths raised the offensive's total toll to 1,031 civilians, including 219 children. More than 4,350 have been wounded.