The packed processions of black-clad worshippers made their way to his gold-domed shrine, carrying flags and crying out, "We sacrifice ourselves for you, Oh Hussein!"
Shia Muslims make the annual pilgrimage to commemorate the martyrdom of Prophet Muhammad's grandson Imam Husayn in the Battle of Karbala in the year 680 by the forces of Caliph Yazid. Hussein's killing has been attributed with cementing the schism between Shiite and Sunni Islam.
The processions usually occur under heightened security as in recent years they have been attacked by extremist militants from the Sunni movement.
The following year, 2005, during a different religious holiday, rumors of a suicide bomber caused a mass stampede on a Baghdad bridge crossing the Tigris River. Another official told the AP that there had been no collapse or crack in the walkway near the shrine. The run is said to symbolize when the maternal cousins of Imam Hussein's half-brother al-Abbas ran from a nearby village to rescue him, only to find out that he had been killed. Numerous faithful beat their chests and lashed themselves with chains in a symbolic expression of grief and regret for not being able to help Hussein before his martyrdom.