Jihadists and rebels captured strategic military positions on the edges of Syria's second city Aleppo on Saturday, turning the tables on Russian-backed regime forces besieging the city.
To the northeast, a Western-backed alliance of Arab and Kurdish fighters scored a major victory against the Islamic State group in the town of Manbij after a fierce two-month battle.
The developments have rocked the key northern province of Aleppo, a microcosm of Syria's topsy-turvy, multi-front war that has killed more than 280,000 people.
Rebel and regime forces have fought for control of the provincial capital of the same name since mid-2012, transforming the former economic powerhouse into a divided, bombed-out city.
On Saturday, opposition fighters and allied jihadists captured fresh territory south of Aleppo in a bid to cut off regime forces and open up a new route into besieged rebel-held districts.
"The Army of Conquest on Saturday took control of the armament school, where there is a large amount of ammunition, and a large part of the artillery school" at a military academy south of the city, said the Syrian Observatory for Human Rights.
The coalition of rebels, Islamists, and jihadists "is about to cut off, by gunfire, the supply route into government-controlled districts" of the city, Observatory head Rami Abdel Rahman said.
That road passes through a southwestern suburb of Aleppo called Ramussa and is the last route into the city used by regime troops.
Opposition forces in the city -- encircled by the government since July 17 -- are hoping to expand their control in the area and use that route themselves.
- IS defeat in Manbij -
"The regime forces are in a very difficult position despite Russian air support," Abdel Rahman said.
The former Al-Nusra Front -- renamed Jabhat Fateh al-Sham after breaking from Al-Qaida -- on Saturday announced having captured the two military academies and a third military position.
Drone footage posted by the group online showed a series of explosions in some of those buildings, followed by massive columns of billowing black smoke.
State media reported fighting in the three locations and said the army had dispatched reinforcements to take on "thousands of terrorist fighters".
Regime forces, with air support by key ally Moscow, had initially been able to hold off the rebels, who launched their offensive on Sunday.
Also on Saturday, the US-backed Syrian Democratic Forces handed a major defeat to Islamic State group jihadists in the town of Manbij.
The Britain-based Observatory said the SDF "took control of Manbij on Saturday and are combing the city in search of the last remaining jihadists."
The town had served as a key transit point along IS's supply route from the Turkish border to Raqa, the de facto capital of its self-styled Islamic "caliphate".
The SDF launched its offensive on May 31 with air support from the US-led air coalition bombing IS in Syria since September 2014.
It encircled the town in early June and surged into it later that month, but its assault was slowed by a fierce jihadist fightback using suicide attackers and car bombs
A spokesman for the Manbij Military Council -- a key component of the SDF -- said fighting was still ongoing in the town.
"The battles are continuing near the centre of the town. We are in control of 90 percent of Manbij," Sherfan Darwish told AFP.
Formed in October 2015, the SDF has seized swathes of territory in north and northeast Syria from IS.
Syria's conflict first erupted in March 2011 with anti-government protests but has since evolved into a fully-fledged war largely dominated by jihadist groups.
As well as killing more than 280,000 people, it has forced half the population to flee their homes, including nearly five million seeking refuge in neighboring countries.