The town had previously been held by Al-Nusra Front
Syrian government troops backed by Lebanon's Hezbollah on Thursday took control of the key rebel-held town of Al-Hader, south of Aleppo city, a military source told AFP.
"Syrian troops and allied forces have full control of Al-Hader," the source said of the town, which is around 10km from the key Aleppo-Damascus highway.
Syrian state television, citing a military source, also reported the capture of the town.
The Syrian Observatory for Human Rights monitor said government troops backed by fighters from Hezbollah, the Lebanese Shia militia, had entered the town and taken control of large parts of it.
The Britain-based group said fighting was ongoing, adding that both Syrian and Russian war planes were carrying out strikes in the area.
"The town is the biggest headquarters for rebel forces in southern Aleppo, and capturing it would bring the army closer to the key Aleppo-Damascus highway," said Observatory chief Rami Abdel Rahman.
It was largely controlled by Al-Qaeda affiliate Al-Nusra Front and other allied groups, he said.
Al-Hader has been a key goal of a regime offensive south of Aleppo city launched on October 17 with support from Russian war planes.
It lies around 25km south of Aleppo city, which has been divided between government control in the west and rebel control in the east since shortly after fighting began there in mid-2012.
The situation is largely reversed in the countryside surrounding the city, and a large stretch of the Aleppo-Damascus highway leading from the government-controlled portion of Aleppo south is under opposition control.
The capture of Al-Hader comes after regime forces entered the Kweyris military base in eastern Aleppo province, which had been under an Islamic State group siege for over a year.