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

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

Russia has carried out air strikes on parts of the Syrian city of Aleppo after areas were seized by rebels opposed to the rule of President Bashar al-Assad. Recent days have seen the most significant offensive against the Syrian government in years and the withdrawal of its military from Aleppo,