At least 31 people have been killed in a stampede during the observance by Shi'ite Muslims of a holy day in the Iraqi city of Karbala, the country's health ministry said.
The stampede occurred when part of a walkway reportedly collapsed Tuesday, causing panic as thousands celebrated Ashoura, one of the most sacred religious holidays for Shi'ites.
Pilgrims from around the world gather annually in Karbala, the site of the 680 A.D. killing of the grandson of the Prophet Muhammad. According to Islamic tradition, Imam Hussein was killed in battle by a rival Muslim faction, sealing the rift between Sunni and Shi'ite Muslims, who view Hussein's descendants as the rightful heirs to the prophet.
The health ministry said another 100 people were injured and that the death toll could rise.
Extremist Sunni militants have attacked Ashoura processions in recent years, but Tuesday's commemorations were peaceful until the stampede occurred.
Earlier Tuesday, hundreds of thousands held Ashoura street processions amid tight security in Karbala and Baghdad. Many pilgrims lashed themselves with chains and beat their chests in an expression of regret for failing to help Hussein before his death.
Thousands marched toward the holy shrine of Imam Hussein in Karbala, which had been lit up on the eve of the two-day celebration.