Wednesday's bombing at a military parade killed 10 and left 80 wounded [AFP]

Iran has arrested members of a group suspected to be behind a bomb blast that killed over 10 people during a military parade in the northwestern region, Iranian state television has reported.

"The group that carried out this terrorist attack has been arrested ... and hopefully they will be punished ..." Heidar Moslehi, the intelligence minister, was quoted as saying on Thursday.

The bomb explosion in the city of Mahabad on Wednesday also wounded 80 people.

Iranian authorities blamed the blast on "anti-revolutionary"fighters backed by foreign enemies of the clerical establishment, including the United States and Israel.

No group has claimed responsibility for the blast which occurred during the "Sacred Defence" celebrations, an annual ceremony for the armed forces to commemorate Iran's eight-year war with Iraq in the 1980s.

Moslehi gave no details of those arrested, saying "the blast targeted unity among Shiites and Sunnis in the country".

The government has announced three days of mourning in Mahabad, the capital of a short-lived Soviet-backed "Republic of Kurdistan" in 1946 which was crushed within a few months.

Kurdish separatists

It was also the centre of a Kurdish uprising shortly after the 1979 Islamic Revolution.

Iranian media have often reported clashes between the elite Revolutionary Guards and Kurdish fighters said to be members of the Party of Free Life of Kurdistan (PJAK), an offshoot of the Kurdistan Workers Party which began an armed campaign in 1984 for an ethnic homeland in southeast Turkey and northwest Iran.

Several armed groups hostile to the establishment are active in Iran, including Kurdish separatists in the northwest, Baluch fighters in the southeast and some Arabs in the southwest.

The Sunni Muslim armed group, Jundollah, which Iran says is linked to al-Qaeda, is the most active. It claimed responsibility for a double suicide attack which killed 28 people, including Revolutionary Guards, on July 15 in retaliation for the execution of its leader.