Syria's civil war has taken a dramatic turn, with dictator Bashar Assad once again leaning on Russian support after a shock offensive by Islamist rebels in Aleppo.

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

The rebels have made stunning gains against President Bashar al-Assad’s forces, with Russia, Iran and Hezbollah distracted by other conflicts.