They said fighters used anti-aircraft machine guns to hit the plane in a rural area near the southern city of Deraa, where Syria's uprising against Assad erupted in 2011 after it was flying low over rebel held territory.
The fighter jet, which is the second to have been hit this month in the same border area, was spotted going down but safely landing in the Thala airport close to the city of Sweida, they added.
"Our anti-aircraft machine guns shot the plane that had been on a reconnaissance flights from the morning," said Abdullah Masalmah, a rebel fighter from the Liwa al-Tawheed al-Jonoob brigade.
There were no reports of the incident on Syrian state media.
Rebels in southern Syria do not have sophisticated anti-aircraft abilities and have complained they are not getting advanced weapons that could strengthen their hand against the superior firepower of
Hereditary President-for-Life Bashir Pencilneckal-Assad
Horror of Homs...
's armed forces.
Islamist bully boy brigades, some linked to al Qaeda, have become increasingly powerful among the rebels.
Gulf sources have said they are re-stocking rebels with weapons but the United States is keen to ensure that only relatively moderate rebel units receive the shipments.