Saturday marks the holy day of Ashura for Shi'ite Muslims. It's the most impassioned day of the year for them. Hundreds of thousands of people in countries like Iraq, Afghanistan, Pakistan and Iran flocked to the shrine of Imam Hussein, the grandson of the prophet Mohammed.

Security forces were also on high alert over fears of attacks on Shi’ite processions. Ashura is observed on the 9th and 10th day of Muharram, the first month of the Islamic calender. It marks the anniversary of the Battle of Karbala, where Imam Hussein and his family members were killed.

Shi’ites mourn by crying, flagellating themselves and listening to poems and sermons about how Hussein and his family were martyred.