Dozens of people are reported to have been killed or wounded in a government air strike on a bakery in the central Syrian province of Hama, opposition activists say.
The incident took place in the town of Halfaya, the activists said.
Rebels have been fighting the government of President Bashar al-Assad for 21 months.
Opposition activist groups say more than 44,000 people have been killed, including nearly 31,000 civilians.
One activist told Reuters news agency of the latest air strike: "We cannot get an exact figure yet because we are still confused about which are dead and which are wounded."
There are fears the toll of casualties could be considerably higher.
Rebels of the Free Syrian Army have been making a concerted push recently to take areas of Hama province.Five days ago they declared Halfaya a "liberated area" after taking over army positions there.
The latest violence comes as the United Nations and Arab League special envoy on Syria, Lakhdar Brahimi, arrived in Damascus to discuss ways to end the unrest.
Mr Brahimi, on his third trip to Damascus since taking the post, arrived overland from Beirut because of fighting near Damascus airport.
He is expected to meet Syria's foreign minister and President Assad.