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.

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,