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?

The Syrian regime has rushed in reinforcements to hold off a rebel advance into the Hama countryside, after the insurgents seized the country’s second city Aleppo in the biggest threat to autocratic ruler Bashar al-Assad in years.

A war monitor, the Syrian Observatory for Human Rights, said the insurgents led by Hayat Tahrir al-Sham seized control of Aleppo International airport, the first international airport to be controlled by insurgents. The fighters claimed they seized the airport and posted pictures from there.

Iranian-backed Iraqi militias have deployed in Syria to back the government’s counteroffensive against a surprise advance by insurgents who seized the largest city of Aleppo

The surprise attack, led by the Islamist group Hayat Tahrir al-Sham, was the boldest rebel assault for years in the civil war that has been frozen.

The Syrian military rushed reinforcements to the country's northwest and launched airstrikes on a major city Sunday in an attempt to push back insurgents who seized the country's largest city of Aleppo in a surprise offensive in recent days.

The Syrian military has rushed in reinforcements to push back insurgents from advancing farther into the northern Hama countryside after they seized Aleppo in a surprise offensive

Warplanes targeted the city of Idlib in an attempt to fend off advances made by antigovernment forces that included a stunning assault on Aleppo.

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,