BEIRUT- A Syrian rebel alliance said it had captured an air base from the army in southern Syria on Thursday, a gain that would compound setbacks for President Bashar al Assad in the area after losing a nearby military base this week. Issam al-Rayyes, spokesman for the Southern Front alliance of rebel groups, said al-Thala air base in Sweida province had been 'liberated'. Syrian officials could not immediately be reached for comment. A second rebel commander however said the base had yet to fall to the insurgents. Bashar al-Zoubi, head of the Yarmouk Army, said he expected that to happen before the day ended.