Eastern Ghouta has been under government siege since 2013 and its estimated 400,000 inhabitants are suffering severe shortages of food and medicine.
Yesterday, a barrage of Syrian artillery fire hit a market in the main Eastern Ghouta town of Douma, according to the Syrian Observatory for Human Rights.
"Nine people were killed, including a woman," the British-based war monitor said.
Another six civilians were killed in artillery fire on the towns of Hammuriyeh, Arbeen and al-Marj. Syrian air strikes killed a child in the town of Zamalka.
Twenty-nine patients, mainly children, were allowed out in December to get treatment under a deal struck between the regime and rebels, but several have already returned.
Eastern Ghouta was one of four "de-escalation zones" agreed under a deal agreed last year between rebel backer Turkey and regime allies Iran and Russia.
But the opposition stronghold remains the target of intense air strikes and a crippling government siege.
Syria's conflict erupted in March 2011 with protests against the government but has since evolved into a ferocious civil war.
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