Among the dead were "five regime troops, including an officer," the Syrian Observatory for Human Rights said.
The attack on the Furqan and Meridian neighbourhoods also wounded at least 30 people, the Britain-based watchdog added.
State television said at least 17 people were killed in what it described as an attack by "terrorists".
Aleppo, which was once Syria's bustling commercial hub, has been one of the main focuses of the 33-month conflict since rebels seized large swathes of the city in an offensive launched in July last year.