State news agency SANA said the explosion took place at a school that had been transformed into "an ammunitions and explosive devices warehouse.
State news agency SANA said the explosion took place at a school that had been transformed into "an ammunitions and explosive devices warehouse left behind by terrorist groups in the Sukkari neighbourhood".
Citing a police source, it said another 33 people were wounded in the blast, four of them critically, but did not specify whether they were civilians or government troops.
The Syrian Observatory for Human Rights monitoring group also reported two killed in the Sukkari warehouse, but said the blast took place as army troops were dismantling explosives.
The Britain-based monitor said one other person was killed when an improvised explosive device detonated in a home in the Ansari district.
Since declaring Aleppo fully under its control on Thursday, Syria's army has been sweeping through former rebel neighbourhoods in search of explosives and mines.
President Bashar al-Assad's win in Aleppo is the most devastating blow to rebel forces since the uprising erupted in March 2011.
For more than four years, the northern city was divided between opposition fighters in the east and regime forces in the west.
On Saturday, six civilians were killed in air strikes on the rebel-held town of Atareb, west of Aleppo city, the Observatory said.
At least two children were among the dead, according to the monitor.
It could not immediately specify who had carried out the air raids, but Russian and regime warplanes typically carry out raids in Aleppo province.
An AFP correspondent in Atareb said military aircraft could be seen circling above the town and a nearby village throughout the day.
Moscow launched its air war in support of Assad's forces in September 2015, marking a major turning point in the regime's fight against rebel groups.