Nearly two dozen civilians are reported to have been killed as Syrian increases its effort to take the last major rebel held enclave outside Damascus.
According to the Syrian Observatory for Human Rights, the toll could rise further as many more people were hurt by artillery shelling on the Eastern Ghouta district.
The British based group says at lleast 127 people, including 30 children, have been killed since the Syrian army backed by Russian jets began its offensive nearly two weeks ago.
Eastern Ghouta is one of several "de-escalation" zones across western Syria, where Russia has brokered deals to ease the fighting between rebels and President Bashar al-Assad's government.
Aid workers say the area is suffering a humanitarian crisis and fear the continuing bombardement will lead to disease outbreaks.
It comes on the eve of the start of U.N.-backed peace talks which are due to begin in Geneva on Tuesday.
Several previous rounds of negotiations have failed to agree a political transition for Syria or a way to stop the violence.