A Syrian warplane crashed northeast of Damascus on Friday and a rebel group accused the al Qaeda-linked Nusra Front of killing its pilot after his capture.

Syrian state media said the crash had been caused by a technical fault and that a search was under way for the pilot, who had ejected. Insurgents said the plane had been shot down, but did not say what weaponry was used.

The rebel group Jaish al-Islam said the pilot had been killed by a Nusra Front fighter while being held at a joint command centre. Jaish al-Islam had earlier said he would be handed over to them because they had shot down his plane.

Jaish al-Islam, which controls territory on the Syrian capital's eastern and northeastern outskirts, had earlier circulated a photo that it said showed the pilot.

"We call on the Nusra Front and Ahrar al-Sham to issue a statement explaining what happened and also call on them to hand over the pilot's body," a Jaish al-Islam statement said. Ahrar al-Sham is another large insurgent group.

Rebels shot down at least two warplanes earlier this year. The Syrian government said one of them had been downed by an anti-aircraft missile, but rebels said they had used anti-aircraft guns.

Foreign-backed rebels have long demanded anti-aircraft missiles to help them fight off air raids by Syrian and Russian forces.

Russia has been a major ally of Syrian President Bashar al-Assad and arms supplier in the civil war, now in its sixth year.