Activists say at least 15 opposition fighters have been killed in a battle with Syrian government troops for a military helicopter base in the country's north.

The Britain-based Observatory for Human Rights says fighting between rebels and President Bashar Assad's troops is raging around the Mannagh base in the northern province of Aleppo.

The activist group says the government deployed fighter jets to the area late on Monday, pounding rebel positions around the helicopter base, which is located near Syria's border with Turkey.

The Observatory said Tuesday that at least 15 rebels have been killed in the fighting.

Rebels have repeatedly targeted Assad's air bases around the country in their 2-year-old campaign to topple his regime. More than 70,000 people have been killed since the conflict started in March 2011.