BEIRUT : Helicopters dropped TNT-packed barrels on a vegetable market and next to a hospital in Syria's northern city Aleppo Saturday, killing at least 25 civilians including two children, a watchdog said.

"The number of people killed has risen to 25 including two women, four children, a teenager and a media activist," the Syrian Observatory for Human Rights said, updating an earlier toll. "The number is likely to rise further because several people have been critically injured," the Britain-based group added. The Syrian Revolution General Commission, a network of activists on the ground, called the bombing a "massacre". "The raid targeted a crowded market where people were buying vegetables and home appliances," it said. "Many buildings have been damaged, and one collapsed."

The Observatory and activists in Aleppo say President Bashar al-Assad's regime has waged a massive aerial offensive against the city and nearby villages since December 15, killing more than 400 people, mostly civilians.

Warplanes have launched rockets and helicopters dropped so-called barrel bombs, often on densely populated rebel-held areas, terrorising residents. Rights organisations and Arab and Western countries have condemned the offensive as "indiscriminate" and "unlawful", but Assad's regime says it is targeting "terrorists". Activists distributed footage of the badly damaged market area. "We have picked up pieces of children's bodies - they were there with two women and a man," said one man, pointing at a destroyed vehicle. "Inside the car there were bodies of women with their heads severed. We put the remains in bags - May God take his vengeance against you, tyrant," he added of Assad. Observatory director Rami Abdel Rahman said the regime is using the same tactic for Aleppo as it has for other besieged rebel-controlled areas.

"The regime wants to take back rebel areas through an air offensive, terrorising the civilians and pushing out the rebels," said Abdel Rahman. "It will then try to besiege these areas, even if it doesn't have enough troops for that right now." Activists said Ahmad al-Hajji, an independent anti-regime activist, was killed in the market attack. They distributed a recording of Hajji taking part in a discussion on Syria that was broadcast on an official television channel months into the anti-Assad revolt.