The UK-based Syrian Observatory for Human Rights, which relies on a network of spies working for the foreign-backed opposition, accused the Syrian army of launching the attack with helicopters on Tuesday.
It added that the bombs targeted a compound in the Masakan Hanano district of the city.
The group also said that more than 150 people have been killed in Aleppo over the past four days in a string of barrel bomb attacks and other airstrikes.
Damascus has not commented on the incident yet.
Meanwhile, US Secretary of State John Kerry criticized the Syrian government over the alleged barrel bomb campaign targeting Aleppo.
This came as Washington itself stands accused of arming militants fighting against the government of President Bashar al-Assad.
A British defense study showed that about 100,000 militants, fragmented into 1,000 groups, are fighting in Syria against the government and people.
The extracts of the study by defense consultancy IHS Jane's were published on September 16, 2013.
IHS Jane's estimates that some 10,000 militants are fighting for groups affiliated with al-Qaeda and the rest fight for different militant groups.
The analysis also said that a large number of extremists from foreign countries are active in Syria.
Syria has been gripped by deadly unrest since March 2011. According to reports, the Western powers and their regional allies -- especially Qatar, Saudi Arabia, and Turkey -- are supporting the militants operating inside Syria.
According to the United Nations, more than 100,000 people have been killed and millions displaced due to the violence.
