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.

The insurgent offensive, shocking for its speed, has posed the most serious challenge to President Bashar al-Assad in years.

The surprise attack, led by the Islamist group Hayat Tahrir al-Sham, was the boldest rebel assault for years in the civil war that has been frozen.