The jihadist Islamic State of Iraq and the Levant (ISIL) has taken most of the town of Al-Bab in Syria's Aleppo governorate after fighting with opposition militants.
The advance by the group in the country's turbulent north comes after 10 days of fighting pitting Islamist opposition forces against the Al-Qaeda inspired organisation that has killed nearly 700 people.
Opposition Observatory told AFP that "ISIL has seized almost complete control of the town of Al-Bab, northeast of Aleppo city", adding that "the sound of shooting can still be heard in Al-Bab, but it's not clear if that is from continuing clashes or mopping up operations".
Elsewhere in the province, the Observatory said opposition militant groups battling ISIL were progressing in the town of Jarabulus, near the Turkish border.
Observatory said "overnight, fighting continued in Jarabulus between ISIL and the Islamic Front and other rebel groups, with the latter progressing", adding that "the fighting in Jarabulus resumed after a deadline given by rebels for ISIL fighters to withdraw from the city passed without them leaving".
Fighting between ISIL and opposition groups also erupted again in the northwestern province of Idlib.
Jihadist foreign fighters were widely welcomed by opposition militants when they first entered the conflict, but have experienced a backlash against their reported abuses of civilians and rival groups.
On Sunday, ISIL in Raqa issued a statement accusing opposition groups of fighting against it to please the West and other "apostate" nations before a scheduled peace conference in Switzerland this month.