At least 70 rebels were killed in airstrikes that struck Syria's Aleppo city, the state-run news agency Sana reported on Thursday.As many as 74 airstrikes were conducted over the past 24 hours against military bases that the rebels have captured in the south of Aleppo, it said, adding that several rebel weaponry and vehicles have also been destroyed.The escalated air raids came as part of the Syrian military counter-offensive against a series of military bases controlled by the rebels in the city.Earlier this month, Jaish al-fateh, a coalition of several radical religious rebel groups, unleashed a wide-scale offensive against several adjacent military bases in southern Aleppo, trying to break a government siege on rebel-held areas.