Syria tells civilians to leave Aleppo's Kurdish areas
Thousands have already fled the area following clashes between the army and Kurdish-led forces that have killed more than a dozen people.
The violence comes as the two sides struggle to implement a March deal to merge a semi-autonomous administration and military run by the Kurds in Syria's north into the country's new Islamist government.
Shops, universities and schools were closed for a second consecutive day in Aleppo on Thursday, according to AFP correspondents on the ground.
The violence erupted on Tuesday and have left 17 people dead.