BEIRUT (AFP) - Kurdish militia in Syria wrested control of a dozen villages from the extremist Islamic State in Iraq and Syria (ISIS) group either side of the terror group's bastion province of Raqa on Sunday, a monitor said.

The Syrian Observatory for Human Rights said the Kurdish People's Protection Units, backed by air strikes from a US-led anti-ISIS coalition, seized eight villages from ISIS on the western edges of Raqa province.

"Kurdish units and their allies advanced and took control of at least eight villages southeast of Kobane, amid air strikes by the international coalition," the Britain-based monitor said.

Kurdish militia and Syrian rebels pushed ISIS back from Kobane, which lies in northern Aleppo province on the Turkish-Syrian border, in January.

Since then, YPG units have edged east towards Raqa, which IS declared the capital of its self-styled caliphate last year.

Syrian Kurdish fighters also seized control of four villages from IS near a border town in Hasakeh, east of Raqa, the Observatory said.

"There are still clashes between the YPG and IS southwest of Ras al-Ain," the monitor said, adding that at least eight IS fighters and three Kurdish militia were killed in the fighting.

On Saturday, ISIS launched an assault on Hasakeh's provincial capital, advancing to within four kilometres of the key city.