Police in Iran killed four Daesh suspects, two of which were foreigners, in the southern province of Hormuzgan, an Iranian news agency said on Monday.
Police also seized explosives, guns and the group's flag, it added.
A major security operation is underway in Iran after 17 people were killed last Wednesday in suicide bombings and gun attacks in Tehran.
Attacks were the first to be claimed by Daesh inside the country.
"Police forces clashed with the four men and killed them in a mountainous area in southern Iran," the semi-official Tasnim news agency quoted a local police chief as saying.
Two of those killed were not Iranian, he said.
Guns, ammunition, explosives and the flag of Daesh were seized during the operation, Tasnim reported, citing the police chief.
Over 50 suspects arrested
Hormuzgan, which borders Pakistan and Afghanistan, is home to a Sunni minority and has seen previous clashes between security forces and insurgent groups.
The authorities say Iranian security forces killed the mastermind of the attacks on Saturday and that more than 50 suspects have been arrested around the country.
Iran accuses Saudi Arabia of funding hardline Sunni militants, including Daesh, and in the wake of last week's attack pointed the finger at its regional rival.
Riyadh has denied involvement in the attacks.