A Syrian coalition of jihadists and Islamist rebels on Saturday seized key positions south of Aleppo as they press a major offensive to break the government siege of the city, a monitor said.
"The Army of Conquest on Saturday took control of the armament school, where there is a large amount of ammunitions, and a large part of the artillery school", the Syrian Observatory for Human Rights said.
The coalition "is about to cut off, by gunfire, the supply route into government-controlled districts" of the city, Observatory head Rami Abdel Rahman said.
The road, which passes through a southwestern suburb of Aleppo city called Ramussa, is the last open route into Aleppo city.
If the rebels capture it, they would simultaneously cut off regime forces and open up a new road for their own besieged forces in the city's east.
The former Al-Nusra Front -- renamed Jabhat Fateh al-Sham after breaking from Al-Qaeda -- on Saturday announced having captured the two military academies and a third military position.
State television, meanwhile, reported fighting in the three locations.
"The regime forces are in a very difficult position despite Russian air support," Abdel Rahman said.
Once Syria's economic powerhouse, Aleppo has been roughly divided into a rebel-held east and regime-controlled west since 2012.
The jihadist and rebel advance comes three weeks after regime forces backed by Russian air strikes besieged the city's opposition-held districts, raising fears of a humanitarian crisis there.
The jihadists and rebels have been pressing an offensive to break the siege.
More than 280,000 people have been killed since the conflict started with the brutal repression of anti-government protests in 2011.
Russia launched air strikes in Syria in support of the regime in September last year.