Iran on Tuesday said it has arrested three militant groups planning attacks on Shi’ite Muslims at the annual pilgrimage of Arbaeen.
The Arbaeen marks the end of a 40-day mourning period for Imam Hussein, the grandson of the Prophet Mohammad.
Hundreds of thousands of Iranians travel to the Iraqi city of Kerbala each year, where Shi’ites believes the remains of Imam Hussein are entombed.
Iran’s Intelligence Minister Mahmoud Alavi, visiting in the Iran-Iraq border area, was quoted by state television as saying that “three terrorist groups that wanted to target Arbaeen mourners were arrested.”
He did not disclose precisely when and where the arrests had taken place.
Shi’ites are considered apostates by hardline Sunni Islamist insurgents in Iraq.
Armed Sunni groups in Iran have also increased attacks on military and civilian targets in recent months.
Iran stepped up security in border areas after five gunmen killed 25 people at a military parade in the southwest in September.
Islamic State militants and an Iranian ethnic Arab opposition movement claimed responsibility for the attack, but neither claim provided convincing evidence.
At least 10 Iranian security personnel including Revolutionary Guards were kidnapped on the border with Pakistan recently.
A Sunni separatist group said it had seized them as revenge for the oppression of Sunni Muslims.