Syrian rebels have launched their first major offensive in the country in four years, claiming to have beaten government forces back several miles and captured a dozen villages west of Aleppo.

The surprise assault occurred around Aleppo, a government-held city and one of the focal points of fighting in Syria’s civil war.

Syrian rebels in the last opposition enclave in northern Syria launched on Wednesday a wide-scale military operation against the Syrian army and seized territory in the first such advance in years, army and rebel sources said.