The fighting between the al-Qaida-linked Islamic State of Iraq and the Levant 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. Since the violence started, it has largely overshadowed the broader battle against the government.

The British-based Syrian Observatory for Human Rights activist group said Sunday that at least 697 people have been killed since the clashes began Jan. 3. The toll includes 351 fighters from the Islamist and mainstream opposition brigades, 246 from the “Islamic State,” and 100 civilians.

The al-Qaida-linked 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.

While the rebel infighting has grabbed the spotlight over the past nine days, the fight against the government has raged on across the country. In the central city of Homs, government shelling killed more than 20 people Saturday in the rebel-held Waer neighborhood, the Observatory said. It warned that the death toll could rise because dozens of people were critically wounded in the bombardment.

Another activist group, the Local Coordination Committees, also reported the shelling in Waer. Syrian rebels also have targeted Assad-loyal areas with indiscriminate mortar fire. On Sunday, Syria’s state media said rebel-fired mortar shells killed two people in the pro-government Zahra area of Homs.