Syrian government helicopters have dropped TNT-packed barrels on a vegetable market and next to a hospital in the northern city of Aleppo, killing at least 25 civilians, including children, activists reported.

The Syrian Revolution General Commission, a network of activists on the ground, described the bombing in Tareeq al-Bab district on Saturday 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."

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President Bashar al-Assad's regime has waged a massive aerial offensive against Aleppo and nearby villages since December 15, killing more than 400 people, most of them civilians, according to opposition activists.

Warplanes have launched rockets and helicopters dropped so-called barrel bombs on rebel-held residential areas, often densely populated.

“Being at the frontline these days has become safer than being in civilian areas," Adel Festok, a fighter in Aleppo, told Al Jazeera.

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".

Activists said Ahmad al-Hajji, an independent anti-regime activist, was among those killed on Saturday.

Activists distributed a recording of Hajji taking part in a discussion on Syria that was broadcast live on state television in 2011, a few months into the country's uprising.

"Stop treating us like idiots," Hajji had said, calling on "all media [in Syria], both public and private... to show how the demonstrations are being suppressed. We should be protecting these demonstrations."

Syria's war broke out after Assad's regime unleashed a brutal crackdown against dissent when a popular revolt erupted, calling for change.

Source: Al Jazeera and agencies