Diminished support for the Syrian government from Iran, Hezbollah and Russia enabled opposition forces to take the initiative and seize new territory.

Syrian President Bashar al-Assad sought to shore up support from his allies Sunday, after a monitor said a shock rebel offensive saw government forces lose control of Aleppo for the first time since the start of the country’s civil war.

Iran has thrown its support behind Syria's government after thousands of insurgents took control of the country's largest city of Aleppo.