Iraqi officials say bombings have killed at least 38 people and wounded more than 100 others.
Authorities say back-to-back explosions rocked the city of Hillah, while another bomb blast erupted in the Shi'ite Muslim holy city of Karbala. Thursday's bombings come just two days after car bombs targeted a Shi'ite procession in Baghdad, killing 12 people.
Both cities are part of Iraq's Shi'ite core located in the country's south. Shi'ites participating in religious events are often targeted by Sunni Muslim extremists.
Shi'ite Muslims marked the Ashura holiday near the shrine of Imam Hussein in Karbala on Saturday. Shi'ite pilgrims flock to the holy city during the 40-day mourning period after Ashura.
Elsewhere in Iraq, authorities say a suicide bomber killed three people when he drove his car into a checkpoint in Fallujah. To the north, a car bomb targeting a police patrol in Mosul killed two people.