'Sunni Islamist insurgents such as al-Qaeda frequently hit Shi'ite gatherings with suicide bombers, grenades and shootings in the hope of restarting the bloody sectarian strife that nearly tore Iraq apart in 2006-07.
Pilgrims in Kerbala complained bitterly that the government had failed to protect the millions of people gathered for the festival.
"When I left my house four days ago, I never stopped thinking about getting killed. I lost my brother last Ashura ... and I always say I could be next," said Jasim Mohammed, a civil servant, referring to another Shi'ite ritual, Ashura.
"We will never bow to terrorists. Today I'm coming to Kerbala to practice my rituals and soon I will vote with same determination." '