After U.S.-backed Kurdish forces drove Islamic State militants from the Iraqi city of Sinjar this month, some of the fighters involved began looting houses of Sunni Arabs suspected of ties to the extremist group.

A week later and about 200 miles to the southeast in the oil-rich region of Kirkuk, Kurdish fighters expelled about 60 Sunni Arab families who had remained in the ruins of one village, according to local officials and residents. The Kurds suspected some male relatives of those families of fighting with the Sunni radicals of Islamic State.

Sunni Arab officials and residents in Iraq accuse Kurds of exploiting the war with Islamic State to grab land. In Syria as well, some Sunni Arabs are either fleeing, being forced out or are blocked from returning to areas seized by Kurds or Iran-backed groups, according to residents and some of the Kurdish fighters themselves.