Hundreds of thousands of Shi'ite pilgrims have descended on the Iraqi holy city of Karbala, for ceremonies marking the 7th century martyrdom of Imam Hussein - one of Shi'ite Islam's most revered leaders.
A sea of black-clad pilgrims thronged the streets of Karbala Wednesday to mark the Ashura festivities Thousands of undercover police mingled with the the crowds to prevent attacks by Sunni insurgents that have killed more than 200 Ashura worshippers in Karbala and Baghdad in the past two years.
Officials expect two million pilgrims to join the main observances Thursday in Karbala.
Police in Baghdad also imposed tight security in Kadhimiya district - another site of Shi'ite pilgrimage - and set up checkpoints across the city.
In other developments, U.S. officials say a U.S. Marine has died from wounds from a roadside bomb that exploded during combat operations Monday near Baghdad.
Some information for this report was provided by AFP, AP and Reuters.