Iraqi police say a rocket attack killed a man from Karabala and wounded four people in the shrine city on December 12 as record numbers of Shi'ite pilgrims gathered there for Arbaeen, one of the largest annual religious gatherings in the world.
Police say the rocket was fired from north of the city, where radical Sunni Islamic State militants have battled Iraq's army and Shi'ite militia.
Iraqi Defense Minister Khaled al-Obeidi said on December 11 that more than 17 million pilgrims have traveled to Karbala for Arbaeen, which falls on December 13 this year.
Arbaeen marks the end of a 40-day mourning period for the anniversary of the death of Imam Hussein, the Prophet Muhammad's grandson and the first Imam of Shia Islam.
Millions of pilgrims have come from neighboring Iran, a predominantly Shi'ite country. Iraq has reportedly waived the $40 visa fee for Iranian nationals.
The festival has been marred by deadly attacks in previous years.