DAMASCUS, Feb. 16 (Xinhua) -- At least 35 Islamic State (IS) militants have been killed in clashes with Syria's main Kurdish armed group in the town of Ayn al-Arab, a monitoring group said on Monday.

The clashes on Sunday in the countryside of Ayn al-Arab, also known as Kobane, also left four fighters of the Kurdish People's Protection Units (YPG) killed, said the Syrian Observatory for Human Rights.

The London-based Observatory said the YPG now controls over 2,000 square km in the northeastern countryside of Syria's northern province of Aleppo.

The Kurdish fighters, backed by several rebel factions, have managed to recapture large swathes of predominantly Kurdish areas from the IS since late January, it added.

Since the town's recapture, YPG forces have been expanding their control from Ayn al-Arab into the surrounding countryside, where they have largely encountered weak resistance from the militants.

The IS unleashed a major offensive against Ayn al-Arab late last year due to the city's strategic importance and location on the Syrian-Turkish borders.

U.S.-led airstrikes and efforts by the YPG and other groups in the city have weakened the IS militant group.

Around 70 percent of Ayn al-Arab has been destroyed due to the months-long clashes, according to the Observatory, which says it relies on a network of activists on the ground inside Syria. Enditem