BEIRUT — Activists say latest clashes in northern Syria between Kurdish opposition fighters and rebels linked to al-Qaida have killed 12 Islamic fighters.

The Britain-based Syrian Observatory for Human Rights said on Friday that the clashes took place overnight in the northeastern Hassakeh province.

The dead were all members of two al-Qaida linked groups, the Islamic State of Iraq and the Levant and the Jabhat al-Nusra.

The rebel-on-rebel violence turned into a war within a war earlier this week after a powerful Kurdish militia called on its supporters to fight al-Qaida-affiliated groups to avenge a recent killing of a prominent political leader.