Yasser al-Aboud, a former Syrian army officer who defected in the early days of the revolt, was killed when leading an assault on Syrian army checkpoints in the town of Tafas, northwest of Deraa on Monday, they added.
Abu Hamza from the militant Falujat Huaran brigade that was involved in the clashes confirmed the report saying that Yasser al-Aboud was killed as he was leading a group of militants against Syrian Army troops.
Aboud was a founding member of the Western-backed Free Syrian Army's military council in southern Syria, which groups several armed brigades.
The Syrian army controls most of Dara'a, the cradle of the 2-1/2-year foreign backed war which started in 2011.
Syrian Army has recently stepped up its mopping-up operations against strongholds of armed militants in different parts of the country, inflicting heavy losses on foreign-backed militants.
RA/NJF