At least five Shiite Muslim pilgrims were killed and 30 injured on Thursday when a bomb exploded in the holy city of Karbala, according to local sources, dpa reported.
Sources told Voices of Iraq news agency that the explosion took place near the Shrine of Imam Hussein.
Nearly 125,000 pilgrims have arrived in the holy Shiite city of Karbala for the Arbaeen pilgrimage, scheduled for Monday, marking the 40th day after the death of Imam Hussein, the Prophet Mohammed's grandson.
Tight security measures have been taken in Iraq's holy sites in preparation for the occasion.
Karbala, said to house the tombs of Imam Hussein, lies 130 kilometres south of the Iraqi capital Baghdad.