Several people were also wounded in the attack on the market in the Halak neighbourhood of northeastern Aleppo, the Britain-based monitoring group said.
It also reported at least 21 people killed in clashes between the jihadist Islamic State of Iraq and the Levant (ISIL) and other rebel groups including the Al-Qaeda- affiliated Al-Nusra Front in the eastern province of Deir Ezzor.
Rebel-held areas of Aleppo have come under massive air assault since mid-December as government forces try to regain full control of Syria's second city and one-time commercial hub.
The Aleppo Media Centre run by local activists said that "two residential buildings were destroyed and several shops set ablaze".
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Activists posted a YouTube video showing an ambulance trying to make its way across rubble to the site and the facades of buildings badly damaged.
Youths are seen carrying the body of a man in a rug as others dig through rubble for victims.
The authenticity of the video could not be immediately verified.
Today's air raids come a day after the Observatory reported that twin air strikes on a school in the Ansari neighbourhood controlled by insurgents killed 18 people, 10 of them children.
The Observatory, which relies on activists and medics on the ground for its reports on the three-year war in Syria, said at least one teacher was also among the dead in yesterday's strikes.
Rebel bombardments of regime-held areas of Aleppo have also intensified in past weeks.
On Sunday, rebels fired mortar rounds into parts of the Old City where government forces are entrenched and into other areas of Aleppo, killing more than 20 people.