The fighting occurred in the Rask region in the southwestern Sistan-Balochistan province, Iranian media said without giving further details.
Last month, state television reported the death of a police officer and five "terrorists", said to be members of the Jaish al-Adl jihadist group, in the nearby Khash region.
Jaish al-Adl is thought to be behind a number of attacks in Sistan-Balochistan in recent years, and Tehran accuses it of ties to Pakistan-based Al Qaeda cells.
Ninety percent of Iran's population is Shiite, but the country has significant Sunni populations in its restive border regions, notably Kurdistan in the northeast, and Sistan-Balochistan and Khuzistan in the southwest.