A government air strike on a bakery in a rebel-held town in central Syria killed more than 60 people today, activists said.
The attack coincided with a visit by the international envoy charged with negotiating an end to the country's civil war.
The strike on the town of Halfaya left scattered bodies and debris up and down a street, and more than a dozen dead and wounded were trapped in tangled heap of dirt and rubble.
The attack appeared to be the government response to a newly announced rebel offensive seeking to drive the Syrian army from a constellation of towns and village north of the central city of Hama. Halfaya was the first of the area's towns to be "liberated" by rebel fighters, and activists saw today's attack as payback.
"Halfaya was the first and biggest victory in the Hama countryside," said Hama activist Mousab Alhamadee via Skype. "That's why the regime is punishing them in this way."
The total death toll remained unclear, but the Britain-based Syrian Observatory for Human Rights said more than 60 people were killed. That number is expected to rise, it said, because some 50 of those wounded in the strike are in critical condition.
Amateur videos posted online showed residents and armed rebels rushing to the scene. One stopped to cover a mound of human flesh lying in the street with his coat.
More than a dozen dead or seriously wounded people lay in the street near a simple, concrete building, some in puddles of blood. Near its front wall, bodies jutted from a pile of dirt and rubble on the pavement.
Rebels screamed in distress while trying to extract the bodies, while others carried away the wounded.
It was unclear from the videos if the building was indeed a bakery. Nearly all the dead and wounded appeared to be men, some wore camouflage, raising the possibility that the jet had targeted a rebel gathering.
For the past week, rebels have been launching attacks in the area, most notably in the nearby village of Morek, where they hope to seize control of the country's main north-south highway, preventing the regime from getting supplies to its forces further north in the provinces of Idlib and Aleppo.
Yesterday, one rebel group threatened to storm two predominantly Christian towns nearby if their residents did not "evict" government troops they said were using them as a base to attack nearby areas.
The activist accounts could not be independently verified due to restrictions on reporting in Syria.
The attack coincided with the start of a two-day visit by Lakhdar Barhimi, who represents the UN And the Arab League, to meet with top Syrian officials.
Mr Brahimi has made little apparent progress toward ending Syria's crisis since assuming his post in September, mostly because the sides appear more interested in fighting it out than in sitting down for talks.
In a lengthy news conference today, Syrian Information Minister Omran al-Zoubi repeated the Syrian government's line that it is fighting terrorist groups backed by foreign powers who seek to destroy Syria.
Mr Al-Zoubi said the government was willing to engage in dialogue but said the other side wasn't.
Rebel groups refuse to talk to Mr Assad, saying too many people have died for him to be considered part of the solution.
Violence raged elsewhere in the country today. Anti-regime activists reported government air strikes on suburbs east of the capital and the northern province of Aleppo.
Air strikes on the town of al-Safira, south of Aleppo, killed 13 people, including a mother and five daughters from one family, a local activist named Hussein said.
The town lies next to a large military complex with factories and artillery and air defence bases.
The Observatory said at least 10 rebels and an unknown number of government troops were killed in clashes in Afreen, near Aleppo, Syria's largest city, as rebels sought to storm an army base there.