Backed by tanks and artillery, Syrian regime troops have unleashed what residents in Aleppo called "the heaviest barrage in more than a year" on rebel-held areas around Aleppo's International airport.
Assad forces, stationed at the airport, concentrated their assault on the nearby rebel-held "Brigade 80" base in an attempt to retake it. The brigade was an air defence force with the main task to protect the international airport and Nairab air base.
Government victory there would mean cutting the rebel's route between Aleppo city and the opposition-controlled town of al-Bab, about 30km from the Turkish border.
The assault began at about 5:30 local time (3.30 GMT).
"We did not see it coming. The attack came as a real shock to us," a rebel fighter, who is based 3km from the airport, told Al Jazeera.
"There is an insane campaign going on. The regime is employing a scorched earth policy."