A senior rebel commander in southern Syria was killed in fighting with government troops in the town of Tafas on Monday, sources on both sides.
Lieutenant Colonel Yasser Abbud, "leader of the Fallujah-Houran brigade... was killed fighting against regime troops in Tafas", a spokesman for the rebel Military Council in the southern province of Daraa told AFP.
Better known by his nom-de-guerre Abu Ammar, the commander "headed the operations room in Daraa province," which borders Jordan.
State television also reported the commander's death, describing him as a "criminal, treacherous... deserter".
An activist on the ground said Abu Ammar was "one of the most effective commanders on the ground, and one of the most honest of the (mainstream rebel) Free Syrian Army's officers".
News of his death came hours after government warplanes carried out four strikes on areas southeast of Damascus.
The strikes targeted areas where rebels had seized key regime positions at the weekend, the Syrian Observatory for Human Rights said.
The rebels had pushed forward in the area after a suicide bomber from the Al-Qaeda-linked Al-Nusra Front blew up a vehicle at a checkpoint between rebel-held Mleha and government-held Jaramana on Saturday.
Observatory chief Rami Abdel Rahman said that the rebel advance threatened to isolate Jaramana, a mixed Christian-Druze town which is a key government stronghold in the southeastern suburbs of Damascus.
Southwest of the capital, government troops pressed an assault on the besieged rebel-held town of Moadamiyet al-Sham, sparking fierce clashes on its outskirts, the Observatory said.
The town was one of a number of suburbs of the capital hit in an 21 August sarin gas attack, blamed by the opposition on the regime, which led to a US-Russian deal under which Damascus agreed the following month to hand over its chemical arsenal for destruction.