Kurdish People’s Protection Units (YPG) soldiers walk near the town entrance circle heading to their strongholds in Kobani, Syria.

Kurdish fighters aided by Russian bombing and their allies have captured a former military air base in northern Syria near the border with Turkey, a monitor and rebels said on Thursday.

Abdul-Jabbar Abu Thabet, a local rebel commander in the Aleppo province, said Thursday that Mannagh air base fell to the People’s Protection Units, or YPG, and their allies after fierce battles.

The Britain-based Syrian Observatory for Human Rights said the offensive came as warplanes believed to be Russian carried out 30 airstrikes in the area. It said the air base and a nearby village, also called Mannagh, fell late Wednesday.

With Syrian troops backed by Russian warplanes waging a major offensive between the northern city of Aleppo and the Turkish border, the Kurds appeared to be exploiting the chaos to expand their nearby enclave, known as Afrin.

Rebels say the Kurdish YPG militias have been taking advantage of their preoccupation with fending off a Syrian army ground offensive launched last week in the northern Aleppo countryside to gain ground in the area near a main border crossing with Turkey.

Kurdish fighters based in their stronghold in the city of Afrin, south of rebel-held Azaz, have grabbed a string of villages that rebels have been forced to evacuate to confront advancing Syrian troops coming from the south.

Russian bombing had allowed Syrian troops supported by Iranian-backed Shiite militias to reach almost 25 km (16 miles) from the Turkish border, the closest they have come in more than two-and-a-half years.

This allowed them to rupture a main rebel supply line between the border and portions of the city of Aleppo which insurgents control. The army with the help of its allies is now seeking to regain full control of whatwas once the country’s most populous city.