The Britain-based Syrian Observatory for Human Rights says rebels stormed parts of the Taftanaz air base in the northwestern province of Idlib before withdrawing.
The state-run SANA news agency said government forces protecting the base "repelled the terrorists' attempt to attack the airport" and inflicted heavy losses.
The Observatory says attacks by the rebels resumed early Thursday in an attempt to capture the base. Several efforts in recent months to take the Taftanaz facility have failed.
Syrian rebels have been attacking five air bases in Idlib and the nearby province of Aleppo, trying to chip away at the government's air power, which poses the biggest obstacle to advances by opposition fighters.