Heavy government bombardment across Syria Friday killed at least 56 civilians, more than a quarter of them children, a monitoring group said.
The bloodiest attack was in Eastern Ghouta, a rebel stronghold east of Damascus, where at least 41 civilians were killed, the Syrian Observatory for Human Rights said.
"Regime warplanes targeted the towns of Jisreen and Kfar Batna in the Eastern Ghouta region", leaving 35 killed in those areas, the Britain-based Observatory added.
Six children were among the dead there, and dozens of people were wounded.
But the opposition National Coalition, the leading anti-regime group in exile, blamed the Jisreen strikes on Russia.
"Russian warplanes targeted a public market... leaving 11 killed and 50 wounded" there, the Coalition tweeted.
Another six civilians, including two children, were killed in regime rocket fire on the flashpoint Eastern Ghouta town of Douma, the Observatory said.
Government forces regularly bombard Eastern Ghouta, a populated suburb of Damascus largely controlled by the powerful Jaish al-Islam rebel group.
In a video posted by an online activist group in Jisreen, a distressed man in a debris-strewn street screamed: "Syrian flesh for sale!"
And footage posted by the local SMART news agency depicted men carrying bloodied victims out of destroyed buildings on stretchers as sirens wailed in the background.
Meanwhile, 11 people, including four children, were killed in government air strikes on the central opposition-held town of Talbisseh, the Observatory said.
In the southern province of Daraa, four children were killed when the regime bombarded the town of Hara.
And four civilians died in shelling of the town of Sanamayn, 30 kilometres (20 miles) east of Hara.
Observatory director Rami Abdel Rahman could not specify if that attack was by regime or rebel forces.
Syria's conflict has taken the lives of more than 250,000 people, and another four million have been forced to flee since it erupted in March 2011.