Syrian rebels launched a surprise attack on Saturday and quickly advanced through several provinces in the north and northwest of Syria, including the city of Aleppo, the country’s second largest city.

The advance on Aleppo followed a shock offensive launched on Wednesday, as fighters swept through villages and towns.

Syrian insurgents have marched into wide government-controlled areas in northern Syria, capturing large parts of the country’s largest city and its international airport as well as dozens of nearby villages and towns.