The offensive came as Turkey said it had downed a drone of unknown origin that violated its airspace close to the Syrian border, and a monitor said the death toll in the conflict had risen to more than 250,000.
The Aleppo offensive is the fourth that President Bashar al-Assad’s regime has launched since Moscow began an air campaign on September 30.
Control of Aleppo city, once the country’s economic hub, has been divided between the regime and rebels since mid-2012. The front lines there and in the surrounding countryside have long been static.
A security source said the operation in southern Aleppo province was backed by Russian strikes and fighters from Iran and Lebanon’s Hezbollah militia.
A US official said as many as 2,000 Iranian and Iran-backed forces were aiding the offensive.
The joint command for the Aleppo operation said the army had begun operations on the western and southern outskirts of Aleppo “to liberate you from the armed terrorist groups.”
– ‘Dozens’ of Russian strikes –
The Britain-based Syrian Observatory for Human Rights said the regime had taken control of two villages so far, and that Russian warplanes were pounding two others.
Observatory head Rami Abdel Rahman said Russia had carried out dozens of strikes on the area, which is controlled by a patchwork of rebel groups, including moderates, Islamists and Al-Qaeda affiliate Al-Nusra Front.
A US-designated “terrorist”, a member of Al-Nusra, Saudi national Sanafi al-Nasr was killed in an air strike in Aleppo province along with two other senior Al-Nusra members, the Observatory said.
However, it was not clear if the strike was carried out by Russian or US-led warplanes, it said.
The Aleppo fighting comes a day after government forces began an operation north of Homs city, which lies in the centre of the country and is largely under government control.
The Observatory said all but 17 of the 60 people killed in the fighting Thursday were civilians.