Eight soldiers were also injured in clashes that took place near Marivan city in Kurdestan province where PKK offshoot PEJAK often fight with Iranian security forces.
Gunmen killed at least 11 Iranian Revolutionary Guards in an attack on a post on the Iraqi border on Saturday, official IRNA news agency reported.
Another eight soldiers were injured in the violence that took place in a military base near Marivan city in Kordestan province, provincial security chief Reza Mirzaee said.
Mirzaee, however, did not identify the group involved in the clashes.
No group has yet claimed responsibility for the attack.
Iran's western Kordestan province has been the scene of deadly clashes between the Iranian security forces and the terrorists belonging to PKK-affiliated PEJAK group which is listed as a terrorist organisation by Turkey, Iran and the US.
Earlier this month, the Revolutionary Guards said they had killed three PJAK terrorists in a security operation near the border with Iraq, and nine of them were reported killed by the Guards last month further north on the border.
There is little coordination between Iranian and Iraqi forces over security of the porous border that has also been used by Daesh to enter Iran.
Intelligence Minister Mahmoud Alavi said on Tuesday that security forces in southwest Iran arrested four suspected Daesh terrorists who were planning attacks.
In June 2017, Daesh terrorists carried out coordinated attacks at the parliament building in Tehran and the mausoleum of Iranian revolutionary leader Ayatollah Ruhollah Khomeini south of the capital, killing at least 18 people.