Syrian activists say opposition forces and government troops are fighting for control of a northern airbase.

The Syrian Observatory for Human Rights said rebels launched an offensive Saturday morning to take the Taftanaz airbase.

On Friday, the Observatory said rebels had taken control of a strategic northern town crucial to the government's fierce campaign against rebels in the embattled city of Aleppo.

It said forces loyal to President Bashar al-Assad had completely withdrawn from Saraqeb , where the main highways from Aleppo to Damascus and the Mediterranean coast meet.

Activists said at least 28 soldiers were killed in the attacks on government checkpoints in the area Thursday, leading to the control of Saraqeb.

Government troops have for months been fighting rebel forces for control of Aleppo, Syria's largest city and commercial capital.

The Syrian conflict is entering its 20th month and has caused the deaths of an estimated 36,000 people. Hundreds of people were killed in the past week as the government has stepped up airstrikes against rebel-controlled areas.