Al-Qaeda chief Ayman al-Zawahiri has called on jihadists fighting in Syria’s civil war to unite and fight for the establishment of an anti-US government in Damascus, in a newly released audio message. Syria’s President Bashar al-Assad belongs to the Alawite sect of Shiite Islam, while the divided rebels fighting to oust his regime are mainly Sunni Muslims, including the jihadist Al-Nusra Front.