Eleven rebels have been killed in clashes in northern Syria with Kurdish rebels of the main Kurdish Democratic Union Party (PYD), the Syrian Observatory for Human Rights said on Sunday.
"Fighting last night (Saturday) in the Afrin region between PYD armed wing the People's Protection Committees (YPG) and rebels left 11 dead and 20 wounded" among rebel forces, the Britain-based watchdog said.
It also reported clashes in the same area of Aleppo province several days previously at a checkpoint installed by rebel forces south of the town of Kubani, without saying whether there were any casualties.
Since the beginning of Syria's uprising more than two years ago, the Kurds, who make up about 15 percent of the population, have tried to stay out of the fighting, stopping both rebel and regime forces from entering their areas.
However in some areas, such as the Sheikh Maqsud district of Aleppo city, rebels and Kurdish groups have joined together to fight forces loyal to Syrian President Bashar al-Assad.