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

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.

Syrian armed opposition forces have entered Aleppo just three days into their surprise offensive, marking the first time they have set foot in the country’s second largest city since government forces recaptured the city in 2016.