The bombing took place in Al-Sakhour and Al-Bab neighborhoods of the northern Syrian city, the observatory reported.
Airstrikes in nearby areas also resulted in the deaths of a man and a child, and the wounding of others, the monitoring group said.
In other casualties Tuesday in Syria, nine civilians, including a child, were killed in airstrikes in Deir Ezzor, and three children were killed in Ma'ra Masrin, in the countryside of Idlib province, it said.
The Syrian government's key military backer, Russia, began launching air missions over Syria from an air base in Iran on Tuesday
-- the first time a major power has done so since the 1979 Islamic Revolution.
Russia's Defense Ministry said its bombers had taken off from Hamedan air base in western Iran, hitting targets belonging to Islamist terror groups ISIS and al Nusra Front -- recently rebranded as Jabhat Fateh Al-Sham
-- in the provinces of Aleppo, Deir Ezzor and Idlib.
The raids struck the militant groups' arms depots, command points and training camps in the cities of Serakab, Al-Bab, Aleppo and Deir Ezzor, the ministry said.
Earlier this month, a coalition of Syrian rebels in Aleppo, led by Jabhat Fateh al Sham, broke a crippling government siege of the city
in a victory that Syria's opposition hailed as miraculous.
After punching through government lines, the rebels vowed to continue fighting until the entire city is retaken.
Residents of rebel-held neighborhoods in the east of the city have been facing a crisis with dire shortages of supplies, humanitarian groups have warned.
Robert Powell, global analyst for the Economist Intelligence Unit, said that the rebels' morale-boosting win had allowed for partial relief of the siege.
Despite the rebel vows to continue their fight, "at this stage we are not expecting the opposition to take the entirety of the city given their lack of numbers and the regime's overwhelming air superiority," Powell said.
He said the fight for Aleppo was likely to be pivotal in the outcome of the war, however.
In the event that Kurdish forces to the north of the city created a new front against the Assad regime, "the Syrian army would struggle to hold out on multiple fronts, potentially creating a new dynamic to the conflict that could mark the beginning of the end for the regime," he said.