Syrian and Russian jets are stepping up strikes on opposition forces in northern Syria in retaliation for the sudden offensive that has cost the autocratic regime control of the country’s second largest city,

Syrian rebel fighters began preparations to seize Aleppo a year ago but the operation was delayed by war in Gaza and ultimately launched last week when a ceasefire took hold in Lebanon, the head of Syria's main opposition abroad told Reuters.

Syrian rebel fighters are advancing southward after capturing much of Aleppo, Syria’s largest city, posing the most serious challenge to President Bashar al-Assad in years amid the country’s civil war,