A Syrian Islamist rebel group on Saturday shot down a regime warplane over a village in central Hama province, a monitoring group said.
A pro-government Facebook acknowledged that a MiG-21 warplane went down over Kafr Nabuda but said it was due to "technical difficulties", denying it had been shot down.
The Syrian Observatory for Human Rights said Ahrar al-Sham fired two heat-seeking missiles at the military aircraft flying over Kafr Nabuda.
"The first missile missed but the second one struck the plane," Observatory head Rami Abdel Rahman told AFP.
He said the jet fighter crashed in government-held territory but that the fate of its crew remained unknown.
The pro-government Facebook said the pilot of the MiG-21 "managed to eject safely" and was rescued by Syrian government forces.
Militant groups and rebel fighters have brought down government warplanes several times.
In January 2015, the Islamic State group shot down a regime aircraft over Damascus province, killing the pilot.