The US-backed Syrian Democratic Forces, a group led by Kurdish fighters, said on Monday that one of its fighters was killed and another injured in an attack by ISIS in Syria's eastern Deir Ezzor region.
The SDF was the main fighting force allied to the United States in Syria during fighting that defeated ISIS in 2019 after the group seized swathes of Syria and Iraq.
The SDF reached an agreement in March to integrate with the Syrian government, now led by former opposition groups that toppled President Bashar al-Assad last year.
Syria's new authorities have clashed with ISIS fighters, particularly in the east. Last month ISIS killed five SDF fighters in one of the deadliest recent attacks against the group.