Shiites celebrate the birthday and death of the 12 imams, as well as a number of other occasions. Some of these celebrations extend over more than 40 days, such as the commemoration of the death of the third imam, Hussein ibn Ali, as flocks of visitors pour into the city of Karbala from inside and outside Iraq.
Visitors are mostly Iraqi, but Shiites from Iran, Bahrain, Lebanon and Pakistan, among others, visit Karbala, too.
There are no accurate official statistics of the number of participants in these rituals, but the Shiite Endowment provides estimates according to which the numbers of participants in some of the rituals have reached 20 million.
Shiites of all ages travel hundreds of miles by foot to visit the tombs, as they believe that walking long distances is a show of respect to the high status of the imams.
Massive security efforts on the part of the state are required to protect these processions. With every religious occasion, the security services in the country's central and southern provinces are on alert. Tens of thousands of security agents secure roads and entrances and exits, military vehicles are deployed at intersections and operating rooms conduct continuous intelligence activities.
Sometimes the air force takes part in monitoring the streets, while some provinces also receive military support from other provinces. For instance, in December, Maysan province sent two combat units to Karbala to protect visitors and Nasiriyah province sent two police units and an emergency team to Karbala for the same purpose.
The chief of the Baghdad Operations Command, Abdul-Amir al-Shammari, said in a press conference in Baghdad on May 9 that 75,000 security members were deployed to ensure the protection of visitors during their recent visit of Imam Kadhim's shrine.