Clashes erupted on Saturday between the Iranian Revolutionary Guards and members of the ISIS terrorist group in western Iran, reported Sepah News, the official news site of the Guards.
It added the 21 members of ISIS were arrested.
There was no mention of the number of people killed or wounded in the clash.
The terrorists had crossed Iran’s western border and were placed under surveillance before the Guards attacked them on Saturday morning, said Sepah News.
Armed Kurdish parties have not yet commented on the reports of the clash.
The remote mountainous majority-Kurdish areas near the borders of Iraq and Turkey are the scene of occasional clashes between Iranian forces and ISIS-linked fighters and Kurdish separatists.
In June 2017, ISIS attacked the Iranian parliament in Tehran and the mausoleum of the Islamic Republic’s founder Ruhollah Khomeini, killing at least 18 and wounding dozens.