A Syrian military official and activists say government forces are advancing under the cover of Russian airstrikes toward an air base besieged by the Islamic State group in northern Syria.

The military official said the army captured the village of Bkayze which is about seven kilometers (4 miles) from the air base in Aleppo province. He spoke on condition of anonymity in line with regulations.

Aleppo-based activist Maamoun al-Khatib said on Monday that troops have captured two other villages near the base over the past day.

Since Russian airstrikes began on Sept. 30, Syrian troops have been on the offensive on several fronts around the country, in an attempt to secure supply routes and regain control of strategic areas.

IS has been besieging the air base since 2014.