Government forces backed by Russian air strikes have intensified their military campaign against the city’s rebel-held areas in recent weeks.
The Thuwwar al-Sham rebel group posted a video online that appeared to show a building used by government troops being destroyed by a huge blast.
Dozens of pro-government troops were killed when rebels blew up a tunnel underneath a building in the Syrian city of Aleppo, reports say.
A UK-based monitoring group said 38 troops died in the blast, which it said happened on Thursday.
Aleppo is divided between the rebel-held east and government west.
Hundreds of thousands of people live in the east of the city, which was effectively cut off by government forces earlier this month.