Iraqi soldiers, police and paramilitaries deployed in and around Karbala Tuesday to protect hundreds of thousands of Shiite pilgrims flocking to the shrine city for annual mourning rituals, officials said.
Imam Hussein, the grandson of the Prophet Mohammed, is buried in Karbala, and Shiite pilgrims pack the city each year for Ashura commemorations, which mark his death in the 7th century.
"Our forces from the army and local and federal police took strict security measures culminating today to protect pilgrims in and around Karbala," police spokesman Colonel Alaa al-Ghanimi told AFP.
"Forces from the Hashed al-Shaabi have implemented security measures to control areas in the west of Karbala province," Ghanimi said, referring to an umbrella organisation for pro-government militiamen.
Anbar province, where the Islamic State jihadist group still holds territory, is located to the west of Karbala.
The number of pilgrims participating in the Ashura commemorations is expected to be huge, with Karbala deputy governor Ali al-Mayali saying it was expected to reach three million.
Some 250,000 pilgrims have arrived over the past two days, Mayali said.
Ghanimi said there had been no security breaches so far.
Attacks in Karbala are rare, but the Sunni extremist group IS considers Shiites to be heretics and frequently targets them in attacks.
IS claimed a Sunday bombing in Baghdad that hit a tent where Shiites were distributing refreshments on the occasion of the commemorations for Imam Hussein, killing at least five people.
Imam Hussein was killed in 680 AD by forces of the Caliph Yazid, and his death is marked every year on the 10th day of Muharram, the first month of the Islamic calendar, which is known as Ashura.
Imam Hussein's death was part of a dispute over who should succeed the Prophet Mohammed, which eventually developed into a bitter schism between the Sunni and Shiite branches of Islam.