A Su-22 warplane was shot down on Tuesday by al-Qaida affiliated al-Nusra in Al-Eis district located south of the Syrian city of Aleppo where insurgents are battling Assad forces backed by allied militias, the Syrian Observatory for Human Rights said.
The monitor said a plume of smoke was seen as the plane caught fire before it fell in the Talat al-Iss highland where rebels have come under heavy bombardment by Syrian and Russian jets after they captured the area this week.
The fate of the pilot was not known, the British-based monitor said.
Videos downloaded on social media also showed footage of the plane and pictures of the wreckage of a burnt plane surrounded by rebels.
In a later statement, Syria's Assad regime on Tuesday admitted that one of its warplanes had been shot down over the countryside of the northern Aleppo province.
On Tuesday afternoon, the regime's official SANA news agency quoted an unnamed military source as saying that a regime warplane had been "struck by a surface-to-air missile while carrying out a reconnaissance mission over Aleppo, causing it to crash".
Local sources told Anadolu Agency that opposition fighters had targeted the warplane -- which had been conducting airstrikes in Al-Eis -- with heavy machinegun-fire, causing it to crash in opposition-held territory.
The same sources said the pilot had ejected from the doomed plane and descended by parachute before being detained by opposition fighters, who, they claimed, had taken him to a hospital for treatment.
Syrian opposition forces captured the strategic Al-Eis district earlier this week after fierce battles with regime forces and pro-regime militias.
For the last several weeks, Aleppo's southern countryside has seen fierce fighting between regime forces and armed opposition factions.
Aerial supremacy has been a major advantage for the Assad army that has been battling insurgents seeking to overthrow the Assad regime.
Foreign-backed rebels have long demanded anti-aircraft weapons to offset the impact of devastating aerial raids by Syrian forces and since September Russian planes, but their backers have been wary of delivering weapons that could fall into the hands of hardline groups.
A fragile "cessation of hostilities" truce has held in Syria for over a month as the various parties try to negotiate an end to the five-year-old civil war.
But the truce excludes Daesh and Nusra Front, and air and land attacks by Syrian and allied forces continue in parts of Syria where the Assad regime says the groups are present.