The Opposition fighters seeking to topple President Bashar Al-Assad fought intense battles with his troops on Sunday at two military air bases in northern Syria, activists said. The fighting raged inside the sprawling Abu Zuhour air base in northwestern Idlib province and the Kweiras military air base in northern Aleppo province, according to a report of the Associated Press. The Britain-based Syrian Observatory for Human Rights said at least seven fighters were killed in the fighting in Abu Zuhour, in addition to an unknown number of soldiers. The group, which relies on a network of activists on the ground, said the air force of Al-Assad regime conducted an airstrike on Abu Zuhour village during the fighting to ease pressure on government troops inside the air base. The fighters entered the two air bases on Saturday. Both have been under siege for months.