Rebel-on-rebel clashes have killed nearly 700 people over the past nine days in northern Syria, activists say.
The fighting between the Islamic State of Iraq and the Levant (ISIL) and several Islamist and more moderate rebel brigades has broken out in cities, towns and villages of at least four opposition-held provinces in the north.
It has added yet another layer of complexity to Syria's nearly 3-year conflict, while also overshadowing the broader battle against the government over the past week.
The violence comes less than two weeks ahead of a planned international conference in Switzerland that aims to broker a political solution to the Syrian war.
The opposition British-based Syrian Observatory for Human Rights activist group said on Sunday that at least 697 people have been killed since the clashes began on January 3.
The toll includes 351 fighters from the Islamist and mainstream opposition brigades, 246 from the "Islamic State" and 100 civilians.
The ISIL group has alienated other rebel factions and civilians in the territory under its control by using brutal tactics to implement its strict interpretation of Islamic law.
It has also kidnapped and killed its opponents.
