Shelling by the Syrian regime on the rebel-held area of Eastern Ghouta near Damascus on Friday killed at least 10 civilians, among them six children, a monitor said.
The deaths were the result of the latest bout in an escalating cycle of tit-for-tat attacks between regime forces and the rebels holding the enclave on the Syrian capital's eastern outskirts.
According to the Syrian Observatory for Human Rights, a total of 43 civilians have been killed in the process, most of them in Eastern Ghouta, which has been besieged since 2013 and where humanitarian conditions are dire.
Seven people, including five children, were killed in regime shelling and air strikes in Douma, the main town in the Eastern Ghouta area, Observatory chief Rami Abdel Rahman told AFP.
Elsewhere in Eastern Ghouta, another child was killed in Harasta, he said, adding that two members of the White Helmets rescue organisation were also among Friday's victims.
On Tuesday, the Ahrar al-Sham group, which has positions in Harasta, launched an attack on a regime military base in the area, which is supposed to be a so-called "de-escalation zone" as part of a deal agreed between Russia, Iran and Turkey to bring violence levels down.
The fighting on that front has left at least 37 dead on the regime side, according to the Observatory, a toll the regime has not confirmed. Abdel Rahman said "dozens" of rebels were also killed.
In a hospital in Douma, doctors and nurses were treating a continuous flow of the wounded, as the sounds of crying children echoed through the facility, an AFP correspondent said.
An elderly man with greying hair sought to calm a little girl in tears, her clothes covered in blood, while the bodies of three children killed in the strikes lay inert on a metal table.
Two other injured children sat on a bench, silent, their eyes wide, apparently still in shock. One had a bandaged foot.
Another wounded person had a bandage wrapped around his head, but blood had soaked through it.
On a white hospital bed, Abu Hisham's face contorted in pain as he called out for his wife and children, who had been killed.
"Iman, where are the children?" he cried.
In retaliation for the latest deadly Ghouta shelling, rebels fired rockets into Damascus, killing three civilians on Friday, the same source said.
Six had been killed the previous day, including Syria's national karate coach Fadel Fadi, who died of his wounds after being hit by shrapnel as he left his Damascus sports club, the state-run SANA news agency said.