At least 30 members of the were killed in clashes with Kurdish troops in northeastern Syria on Thursday, a monitoring group said.
The fighting pitted IS militants against members of the Kurdish People's Protection Units (YPG) in the village of Qassiab in Hasakeh province, according to the Syrian Observatory for Human Rights.
The YPG regained control of the village, two days after it was seized by the jihadists, said the Britain-based group, which has a wide network of activists on the ground in Syria.
The Kurds also lost three fighters in the clashes, it added.
Elsewhere, Syrian air force raids killed at least 12 people and wounded dozens in IS-held Al-Bab and Qbasin in Aleppo province, said the Observatory.
Nearly four years of civil war ravaging the country have killed an estimated 200,000 people and also displaced half of the population.