Syrian government aircraft bombed Kurdish positions in the divided northeastern city of Hasakeh on Thursday, the first such strikes against a Kurdish-held area of Syria, an AFP correspondent reported.
The strikes hit three Kurdish-manned checkpoints and three Kurdish bases, the Syrian Observatory for Human Rights said.
They came after heavy clashes broke out on Wednesday between Kurdish fighters who control two-thirds of the city and pro-government militia who control the rest.
The clashes have left 11 people dead -- four civilians, four Kurdish fighters and three government loyalists, a medical source told AFP.
The two sides share a common enemy in the Islamic State jihadist group which controls most of the Euphrates valley to the south but there have been tensions between them in Hasakeh that have sometimes led to armed clashes.
The Kurds, who control much of northeastern and northern Syria along the Turkish border where they have proclaimed an autonomous Kurdish region, recently demanded that the pro-government National Defense Forces disband in Hasakeh.
A government source in the city told AFP that the air strikes were "a message to the Kurds that they should stop this sort of demand that constitutes an affront to national sovereignty."
The Kurdish People's Protection Units (YPG) are a key US ally in the fight
Washington regards them as the most effective fighting force on the ground
in Syria and has provided weapons and special forces military advisers.