More than 21 million Shiite Muslims took part in the Arbaeen pilgrimage in Iraq this year, which reached its peak on Sunday with attendees displaying their support for Gaza.
Arbaeen, which means forty in Arabic, marks the 40th day of mourning for the martyrdom of Imam Hussein, the grandson of the Prophet Mohammed and a founding figure in Shiite Islam.
It is one of the world's biggest religious gatherings and a major event for Shiites, who are the majority in Iraq and Iran.