At least 40 Syrian soldiers were killed on Saturday when rebels detonated explosives packed beneath an army base in Aleppo, activists and rebels said.
The Islamic Front, an umbrella rebel organisation, claimed responsibility for the bombing, though the claim could not be immediately verified.
A video posted on the internet showed a massive blast sending clouds of dust and debris into the air as gunshots rang out in the old Zahrawi area of Aleppo.
The front said 40 government soldiers were killed. The UK-based Syrian Observatory for Human Rights said more than 20 died in the blast and added that fierce clashes had erupted along the divided city’s frontlines, where fighting between rebels and troops has escalated in recent days.