The rapid advance on Aleppo came just four days into a surprise opposition offensive that is the most intense escalation in years in the civil war.

The 13-year civil war in Syria has roared back into prominence with a surprise rebel offensive on one of Syria’s largest cities and ancient business hub.

Syrian opposition forces have taken control of much of the country’s second largest city Aleppo after a lightning advance that killed dozens of government soldiers in a major challenge to President Bashar al-Assad.