At least 90 people were killed and scores of others injured in an air strike on a bakery in Syria's central Hama province, activists said.
Activists on Sunday told Al Jazeera that the death toll was likely to rise in the town of Halfaya, where the strike hit.
"There is no way to really know yet how many people were killed. When I got there, I could see piles of bodies all over the ground. There were women and children," said Samer al-Hamawi, an activist in the town.
Halfaya was seized by rebels few days ago as part of a campaign to push into new territories in the 21-month-old revolt against President Bashar al-Assad.
Another activist said residents picking through the bodies were still determining which were wounded and which were dead.
Mousab al-Hamadee, an activist in the suburbs of Hama, told Al Jazeera that Halfaya and nearby towns have witnessed heavy shelling since rebels began advancing in the province.
"Three days ago, Halfaya was liberated from regime forces. The airstrikes were a message from the regime. They came as a punishment for the residents of the town," he said.
Hamawi said more than 1,000 people had been queuing at the bakery. Shortages of fuel and flour have made bread production erratic across the country, and people often wait for hours to buy loaves.
"We hadn't received flour in around three days so everyone was going to the bakery today, and lots of them were women and children," Hamawi said.
New York-based Human Rights Watch condemned army air strikes on bakeries earlier this year, arguing that in some incidents the Syrian military was not using enough precision to target rebel sites, and in other instances it may have intentionally hit civilians.
Other air strikes on Sunday included a raid in Aleppo province, the UK-based Syrian Observatory for Human Rights said.
"At least 13 people were killed in an air raid on the town of Sfeira," said the group, which relies on a network of doctors, activists and lawyers for its information.
Rebel fighters said they took control of a military base in Aleppo. Around 200 opposition fighters attacked the base in Al Hawa village on Saturday under the cover of fog and rain.
The group seized military vehicles and various types of weapons and ammunition from the base.
Warplanes also hit the town of Saqba in Damascus province, just north of the road linking the capital to the international airport, the Observatory added.
International envoy Lakhdar Brahimi was in Damascus on Sunday to push for a negotiated solution to the conflict. Previous efforts have proved fruitless.