The Syrian army said the jet was shot down with an anti-aircraft missile, which have been long demanded by foreign-backed rebels against devastating aerial raids by Syrian and, since September, Russian forces.
Rebels said the plane was downed with anti-aircraft guns. Their backers, which include Western and Sunni Muslim regional states, have been wary of delivering weapons such as anti-aircraft missiles that could fall into the hands of hardline groups.
Any confirmation the rebels now have the missile equipment would be a major escalation in their weaponry. Syria says an anti-aircraft missile was also used by rebels to shoot down a warplane in western Syria in March.
The aircraft crashed on Tuesday in the Talat al-Iss highland south of Aleppo city, an area where al Qaeda-affiliated insurgents have come under heavy bombardment by Syrian and Russian warplanes since capturing it in recent days, the Syrian Observatory for Human Rights said.
The pilot was seized alive by fighters from al Qaeda’s Nusra Front, the monitoring group said.
Nusra Front later released a video of the wreckage smoldering in an open field, and of the pilot apparently at another location. He gave his name, Khaled Saeed, and said he had carried out bombing runs in the area and was hit by anti-aircraft gunfire.
In a separate statement on Twitter, powerful Islamist group Ahrar al-Sham appeared to take responsibility for the downing of the jet.