BEIRUT — Syrian warplanes have killed dozens of civilians, including more than 20 children, in an intensifying campaign of anti-insurgency airstrikes across the country over the past few days, bombing some targets as families were congregating outside to enjoy a sunny break from prolonged winter storms, activists and international medical aid workers said Monday.
Their version of events was disputed by the Syrian government, which said through the official news agency that the airstrikes had made great progress against what it called armed terrorists fighting against President Bashar Assad.
But the activist accounts were buttressed, at least in one case, by an unusually detailed description from the group Doctors Without Borders, which has been operating quietly in Syrian areas near the Turkish border, where the insurgency is relatively entrenched.
‘‘We could not keep silent,’’ Shinjiro Murata, the head of the Doctors Without Borders mission, said in a telephone interview from Aleppo province. ‘‘We are sure that civilians were deliberately targeted.’’
He said an aerial assault Sunday, which hit an open-air market in the village of Azaz, near the Turkish border, left at least 20 people dead and 99 wounded.
The strike came as many people from around the region were shopping. ‘‘A sunny day,’’ he said. ‘‘Many children were out with their parents.’’
Other signs that children had died in government bomb strikes were seen in videos uploaded on the Internet, although they could not be independently corroborated. In one, a boy’s naked body, thickly coated in gray dust, lay prone amid rubble, in footage that activists said was shot Monday in Moadamiyeh, a suburb southwest of the capital, Damascus, on a street echoing with high-pitched wails and crammed with cinder blocks from collapsed facades. In a room exposed by the blast, a woman could briefly be seen carrying the motionless body of a child.
A second video showed the bodies of half a dozen children laid out on blood-soaked blankets, including one curly-headed toddler no more than 2 years old.
‘‘Let the whole world observe, those are the victims,’’ a narrator said on the video. ‘‘Those are the ones Bashar al-Assad is fighting.’’
The official SANA news service said the Moadamiyeh explosion was caused by an insurgent mortar attack, not by government warplanes. It also said that airstrikes had killed scores of rebels around the country, including many it identified by name.
The tally of children killed in airstrikes, according to activists, included seven killed while playing outside in Hizza, east of Damascus, according to video that showed women weeping over their body parts; three in the northern city of Aleppo; two in an Aleppo suburb; four in Latamna, in Hama province.
In the Azaz attack Sunday, Doctors Without Borders said 20 people were treated for injuries at its hospital in another town, since nearer hospitals had previously been bombed.
The practice of destroying hospitals was corroborated by another humanitarian emergency organization, the New York-based International Rescue Committee, which said in a report Monday that the Syrian authorities were engaged in ‘‘a systematic campaign’’ to hamper medical care through bombing and closing hospitals and intimidating, torturing and killing doctors who help the wounded.