Fierce fighting between ISIL and rival militant groups in Syria in the past nine days have killed at least 700 terrorists and led to the disappearance of hundreds more, an NGO said Sunday.

Fierce fighting between ISIL and rival militant groups in Syria in the past nine days have killed at least 700 terrorists and led to the disappearance of hundreds more, an NGO said Sunday.

"From January 3 to 11, the fighting killed 697 people, among them 351 militant fighters, 246 members of the Islamic State of Iraq and the Levant and 100 civilians," said the opposing UK-based Syrian Observatory for Human Rights, adding that dozens more deaths have yet to be documented.