The al-Qaeda linked Islamic State of Iraq and Syria, or ISIS, has retreated from Aazaz and other key positions in Northern Aleppo, AFP reports.
Their retreat comes in response to an ultimatum  issued by al-Nusra Front earlier this week. Nusra Front, a powerful rival, blames ISIS for the death of Abu Khaled al-Suri, a senior Islamist commander, and threatened to expel ISIS from Syria if it did not appear before an Islamic court.
“ISIS has withdrawn from Aazaz, its most important bastion in Aleppo province, as well as the Minnigh military airport, the Mayer region and the villages of Deir Jamal and Kafin,” said the Syrian Observatory for Human Rights.
“ISIS is heading to areas that neighbor Raqa province where it has its main stronghold in the city of Raqa,” Rami Abdel Rahman, the Observatory’s director, told AFP. 
A war between Nusra Front and ISIS would greatly hinder both groups’ efforts to defeat Assad’s regime.