Mahmoud Atham, an official from volunteer rescue group White Helmets, said the Assad forces targeted Ein Tarma suburb of East Ghouta with 16 airstrikes and 70 missiles.
Atham said 20 others -- including 5 women and 8 children -- were wounded at the attacks.
Last week, two people had been killed in the regime airstrikes.
Eastern Ghouta is one of de-escalation zones announced by Turkey, Russia and Iran in Kazakh capital of Astana in May.
Since civil war in Syria erupted in March 2011, more than 250,000 people have been killed, according to the UN. The Syrian Center for Policy Research puts the death toll at more than 470,000.
