NBC News — Shi'ite Muslims around the world tuesday marked the holiest day on their calendar, the anniversary of the seventh century death of Imam Hussein, the grandson of Islam's Prophet Muhammad. In Iraq, hundreds of thousands of pilgrims gathered at the Holy Shrine in the city of Karbala to observe the day of mourning known as Ashura. Imam Hussein was believed to have been buried at the Shrine following his death at the battle of Karbala in 680 AD.
Around the world, Shi'ites performed the traditional Ashura ritual of beating their heads and chests. For Shi'ites, rituals and observances commemorating their revered saint's martyrdom consist primarily of public expressions of mourning. The day has also been marked with violence, bombings have taken place in several countries. Rival hardline Sunni Muslims view Shi'ites as heretics.