At least 31 people were killed and about 100 were injured, officials said on Tuesday. At least 10 among the wounded pilgrims were in a critical condition, according to the Iraqi health ministry.
It was the deadliest stampede in recent history during Ashura commemorations, when hundreds of thousands of people converge on the city, about 80km south of Baghdad, every year to mourn the martyrdom anniversary of Imam Hussein (AS) and his companions in the 680 Battle of Karbala.
The deadly rush began when part of a walkway collapsed during a procession, causing mass panic among worshippers.
Millions of people in Iran, Pakistan, Afghanistan, India, Bangladesh, and Lebanon also marked the day with mourning ceremonies.