At least 28 civilians were killed on Sunday when Assad missiles rained down on Douma, a besieged Syrian rebel stronghold east of Damascus. Some of the missiles targeted an elementary school.
The rockets and missiles were also accompanied by air strikes, which targeted Douma and the nearby town of Saqba, but it was unclear whether they were carried out by Syrian or Russian warplanes.
The air strikes and rockets wounded dozens.
An activist told AFP:
"One of the air strikes on Douma hit near a school, killing the school's principal."
Government forces regularly bombard Eastern Ghouta, and rebels there fire rockets and mortar shells into the capital.
On Sunday, a young girl was killed and three people were wounded in rebel mortar fire on Damascus, according to the national news agency SANA.
Last month, regime forces and rebel groups tried to reach a 15-day ceasefire in Eastern Ghouta, but the talks failed and violence has resumed.
A local activist group in Douma shared photographs on Facebook of crumbling buildings and bloodied children lying in a makeshift clinic.
AFP contributed to this article.