Dozens of people have been killed in a government air strike on a bakery in the central Syrian province of Hama, opposition activists say.The incident took place in Halfaya, a town recently captured by rebels.If activists’ reports of 90 deaths are confirmed, this would be one of the deadliest air strikes of the civil war.Rebels have been fighting President Bashar al-Assad for 21 months, with opposition groups saying more than 44,000 people have been killed.The latest violence comes as the joint United Nations-Arab League special envoy on Syria, Lakhdar Brahimi, arrived in Damascus to discuss ways to end the unrest.One activist in Halfaya, Samer al-Hamawi, told Reuters news agency: "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."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. I still don’t know yet if my relatives are among the dead.”Unverified video footage purportedly of the incident’s aftermath showed graphic images of bloody bodies strewn on a road outside a partially destroyed building.Rescuers were trying to remove some of the victims buried beneath piles of bricks and rubble.Several badly damaged motorbikes could be seen scattered near the site of the attack which had drawn a number of armed men to the area.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 BBC’s Jim Muir in Beirut says the rebels want to take control of the whole of Hama and link up the territory they control. As has happened many times before, he says, the government has hit back with massive firepower at the areas it has lost.The UK-based opposition activist group, the Syrian Observatory for Human Rights, said there had been other air strikes on Sunday, including one on the town of Safira in northern Aleppo province, which killed 13 people.The Observatory also reported that jets had struck the town of Saqba, just north of Damascus.Meanwhile 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.