A Syrian government air strike on an Aleppo market has killed at least 25 civilians, including four children, a human rights group said Saturday.

The Syrian Observatory for Human Rights also said helicopters dropped TNT-packed barrels near a hospital.

"The number of people killed has risen to 25 including two children, a teenager, a woman and a media activist," the Britain-based group said.

Hassoun Abu Faisal, an activist with the Aleppo Media Center, put the death toll at more than 20, but said medical officials were still tallying the exact figure.

For nearly two weeks, President Bashar al-Assad’s warplanes and helicopters have pounded opposition-controlled areas of the divided city in northern Syria. Activists say the aerial assault has killed more than 400 people since it began December15.

The Syrian Revolution General Commission, a network of activists on the ground, described the bombing as 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."

Human rights organisations as well as Arab and Western countries have condemned the offensive as "indiscriminate" and "unlawful," while Assad's regime says it is targeting "terrorists".

Syria's war broke out after Assad's regime unleashed a brutal crackdown against dissent, when an Arab Spring-style revolt erupted, calling for change.

(FRANCE 24 with AFP and AP)