Syrian troops have pulled out of a major air base in northwestern Syria, state television said on Wednesday, after a two-year siege by Islamist-led insurgents, increasing pressure on government-held coastal areas north of the capital. A group monitoring the war said the Syrian military had been completely driven out of the northwestern province of Idlib after the fall of the base. Rebel sources said al Qaeda’s Nusra Front had played a leading role in the capture of the airport. Nusra is part of a coalition of Islamist groups called the Army of Conquest which has seized most of the surrounding Idlib province. In a newsflash, Syrian state television said the army garrison that had defended the Abu al-Duhur military airport had evacuated the post.