Riad al-Asaad, commander of the rebel Free Syrian Army, was wounded overnight in a blast that hit his car in eastern Syria, the Syrian Observatory for Human Rights watchdog said on Monday.

A government official in Ankara confirmed Asaad had been hurt, saying he had lost a leg in the attack but that he was in "good condition" after being rushed across the Syrian border into Turkey for treatment.

"An explosive device exploded last night near the car carrying Free Syrian Army commander Riad Asaad, who was conducting a tour of the town of Mayadeen in Deir Ezzor province," Observatory director Rami Abdel Rahman told AFP.

Abdel Rahman said Asaad had been wounded in the leg, and a relative of the commander told AFP that he had been transferred to Turkey for treatment after the blast.

A Turkish foreign ministry official confirmed Asaad was taken to Turkey on Monday morning via the Akcakale border crossing and was being treated at a hospital in Sanliurfa province near the border.

"He lost one leg but in general his condition is good," the official told AFP.

Asaad was one of the first officers to defect from the Syrian state military to the rebel forces, joining their ranks in 2011, not long after the uprising began.

He served as commander of the rebel forces but has seen his official role diminished by the creation of a rebel military command headed by Brigadier General Salim Idriss.

Asaad has remained a prominent figure though, regularly appearing with rebel fighters on the ground.