Lions of the East Army and the Ahmad al Abdo Forces claim that the plane crashed in regime-controlled territory near a village on the administrative border between the provinces of rural Damascus and Sweida.
Rebel groups shot down a Syrian regime warplane on Tuesday near a ceasefire zone in the country's south, the factions and a monitoring group, the Syrian Observatory for Human Rights, said.
Two rebel groups that operate in southeast Syria, the Lions of the East Army and the Ahmad al Abdo Forces, issued a joint statement on Tuesday saying they had downed the aircraft.
"The plane was shot down and crashed in regime-controlled territory. We have no information on the pilot," said Fares al Munjed, communications head for the Ahmad al Abdo Forces.
The Syrian Observatory for Human Rights monitor confirmed that the rebel groups had hit the plane near a village on the administrative border between the provinces of rural Damascus and Sweida.
Sweida province is part of a new ceasefire deal negotiated by the US, Russia, and Jordan that went into effect on Sunday.
The deal has brought relative quiet to most of the provinces covered – Daraa, Quneitra and Sweida – though outbreaks of violence have been reported.
In Sweida, regime forces launched an attack on Monday on the Ahmad al Abdo Forces and the Lions of the East Army.
Fighting continued into Tuesday over a series of hilltops and villages in the province, the Observatory and rebels said.
Two shells also landed in Daraa city, but no casualties were reported.
More than 400,000 people have been killed in Syria since the conflict began in March 2011 with anti-regime protests.
Multiple attempted ceasefires, including nationwide truces, have failed to bring a long-term end to the war.