The Syrian Observatory for Human Rights monitor said several IS fighters infiltrated Sarrin, in Aleppo province, and attacked a school being used as a base by the Kurds.
A first attacker blew himself up with the rest then opening fire, the Britain-based monitor said.
At least 10 Kurdish fighters were killed in the blast and subsequent gun battle, along with eight IS members, including the bomber, the Observatory said.
Kurdish forces captured Sarrin Monday, after several weeks of intense clashes with IS.
Its capture cut off IS's main access route to parts of Aleppo province, where the jihadists are fighting both Kurdish forces and rebel groups.