US soldiers patrol an area near the northeastern Syrian town of al-Malikiya (Derik in Kurdish) on December 5, 2021. AFP
The Syrian Democratic Forces (SDF), effectively the armed forces of the semi-autonomous Kurdish region of northeastern Syria, said the raid took place near the village of Busayrah, in Deir Ezzor province.
With backing from the US-led coalition, the raid targeted a hideout used by "a dangerous cell of the terrorist" Islamic State group, the SDF said in a statement.
It said gun battles ensued that led to the killing of five IS members, most of whom were wearing explosive belts.
The Syrian Observatory for Human Rights, a war monitor based in the UK which has a wide network of sources across Syria, said at least four people were killed.
The dead were members of the same family, including two who were shot by helicopter fire as they tried to flee on a motorbike, said Observatory head Rami Abdel Rahman.
Busayrah is a village that lies on the banks of the Euphrates, between the two main cities of Deir Ezzor and Mayadeen, in the middle of IS's original heartland.
US-backed SDF forces flushed out the last rump of what was once IS's sprawling self-proclaimed caliphate in 2019, officially ending the group's existence as a territorial entity.
IS returned to the guerrilla warfare, launching frequent hit-and-run attacks from desert hideouts on either side the border with Iraq.