At least 11 soldiers were killed in clashes with gunmen in western Iran on Saturday, according to the official IRNA news agency.
Another eight soldiers were injured in the violence that took place in Marivan city in Kordestan province, provincial security chief Reza Mirzaee said.
He, however, did not identify the group involved in the clashes.
No group has yet claimed responsibility for the attack.
Marivan city had previously seen deadly clashes between Iranian forces and PEJAK, the military wing of PKK terrorist group in Iran.