Kurdish and Arab forces backed by Russian air strikes captured a strategic air base and the adjacent town in northern Syria from rival anti-government factions, a monitoring group said Thursday.

The Kurdish People's Protection Units (YPG) and Arab allies on Wednesday night expelled Islamist and other rebel fighters from Minnigh air base and the adjacent town, north of Syria's second city Aleppo, said the Syrian Observatory for Human Rights.

"The takeover of Minnigh air base and the adjacent town overnight was backed by at least 30 Russian air strikes," said Observatory director Rami Abdel Rahman.

"There's some coordination between the Kurds and the Russians in Afrin region," he told AFP.

The advance comes after days of fierce clashes that saw YPG forces advance east from the Kurdish stronghold of Afrin and take over a series of villages before reaching Minnigh.

"With the defeat at Minnigh, Islamist fighters lost the only military airport they held in Aleppo province," Abdel Rahman said earlier.

"Minnigh airport lies between two key roads that lead from Aleppo city to Azaz" to the north, giving Kurdish fighters a strategic launching pad for offensives against jihadists further east, he said.

Government forces lost control of the Minnigh airport in August 2013, two years after the uprising in Syria first erupted.

Rebel groups are facing a dual advance by both Kurdish forces coming from the west and regime troops -- backed by a barrage of Russian air strikes -- pressing an offensive north from Aleppo city.

More than 500 people have been killed since the government began its Aleppo assault on February 1, the Observatory said Wednesday.

YPG forces regularly clash with Islamist and jihadist fighters in northern Syria, but its most active front is further east against the Islamic State jihadist group.

Arab rebel groups have accused Kurdish fighters of ethnically cleansing towns to carve out autonomous Kurdish territories, a claim the YPG has fiercely denied.

More than 260,000 people have been killed and half the population displaced in Syria's complex, multi-front war over the past five years.