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.

Scores of people were killed after forces opposed to the government of President Bashar al-Assad overtook a Syrian military base, a monitoring group reported.

By the end of the first day of the offensive, the rebels had advanced into the western Aleppo countryside, taking them within 10km (6 miles) from the outskirts of Aleppo city, according to the UK-based Syrian Observatory for Human Rights (SOHR).

Syrian rebel fighters launched their first major offensive in four years against government positions near Aleppo, claiming to have advanced several miles and captured a string of villages.

Syrian rebels have launched a large-scale attack on regime forces in western Aleppo, according to a Free Syrian Army source and local residents, marking the first major flare-up in years between both sides.

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.

Anti-government rebels in northern Syria have launched a sudden offensive in an effort to capitalize on Israel’s efforts to weaken Iran’s regional proxies.