The Iraqi Interior Ministry said the explosion that occurred between two Shiite holy sites -- the Imam Hussein and the Imam Abbas shrines -- was a suicide attack, CNN reported. Authorities invoked a vehicle ban until further notice.
The attack, which occurred as people made their way to evening prayers, prompted some residents to accuse police of failing to protect them and there were reports of stone-throwing, CNN said.
It was the second attack of its kind in the last two weeks in Karbala, which has generally experienced relative calm. On April 14, a car bombing killed 44 people and wounded scores more.