"Since the rebels have targeted all the supply roads, the airport is the main way for forces in the city to get supplies, so if they can take it over it will be a big blow to the regime," the activist said via Skype, speaking on condition of anonymity out of security concerns.
He and other activists reported a large explosion inside the airport on Friday, though it was unclear what caused it.
Illustrating the danger of the government's air power, anti-regime activists reported a number of deadly airstrikes in different parts of Syria, including in the towns of Azaz and Tel Rifat north of Aleppo and al-Nishabiyeh, south of Damascus.
Rebels also clashed Friday with soldiers inside the Mannagh helicopter base near the Turkish border.
Anti-regime activists say more than 40,000 people have been killed since the start of Syria's crisis in March 2011.
Associated Press writers Maamoun Youssef in Cairo and Vladimir Isachenkov in Moscow contributed reporting.
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