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 rebels have swept through parts of the country at lightning pace, taking control of the the second-largest city, Aleppo. But who are they and what are their aims?

Russia has conducted major air strikes on rebels in Syria after insurgents led by the Islamist Hayat Tahrir al-Sham group swept into Aleppo in what is the biggest challenge to its ally President Bashar al-Assad in years.

At least 372 people have been killed since rebels launched a surprise offensive on Wednesday, according to observers.

Recep Tayyip Erdoğan, Turkey’s president, has said that the rebel advance into Syria will aid the “voluntary return” of migrants from within his country.

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,

The Syrian authorities announced on Saturday a "temporary troop withdrawal" from the city of Aleppo in the country's northwest to prepare a counterattack against the rebels. Source: Reuters Details: The military said the withdrawal is part of an effort to regroup before reinforcements arrive to launch a counterattack.

Syrian opposition fighters have pushed Assad’s forces out of Aleppo, allowing exiled residents to return for the first time in eight years.