Ten people have been killed and 57 more injured in a bomb blast on a military parade in the northwestern Iranian town of Mahabad, according to Arabic-language television, Al-Alam.
The attack on Wednesday took place as Iran marked the 30th anniversary of the start of the eight-year Iran-Iraq war.
"The explosion happened in the morning as people were watching the military parade..." Al-Alam said.
Vahid Jalalzadeh, the provincial governor, confirmed the casualties to the official IRNA news agency.
"Counter-revolutionaries committed this savage act with the aim of taking revenge on the people of Mahabad" in West Azarbaijan province, Jalalzadeh said. Another Iranian politician blamed "foreign elements".
Military parades were being held all across Iran to mark Defence Week.
Western Iran, which has a sizeable Kurdish population, has seen deadly clashes in recent years between the Iranian security forces and Kurdish rebel groups, mainly the Party of Free Life of Kurdistan (PJAK) operating from bases in neighbouring Iraq.