BEIRUT — A Syrian activist group says a clash between army defectors and troops in the northwest of the country has left at least 15 people dead.

The British-based Syrian Observatory for Human Rights says Saturday's pre-dawn fighting in the city of Idlib has killed seven soldiers and policemen, as well as five anti-government army defectors and three civilians.

The U.N.'s top human rights official said this week that Syria is in a state of civil war, and that more than 4,000 people have been killed since mid-March.

Until recently, most of the bloodshed in Syria was caused by security forces firing on mainly peaceful protesters, but there have been growing reports of army defectors and armed civilians fighting regime forces.