Deadly attacks targeting Iraq's majority Shi'ite community killed at least 33 people on October 20.
A suicide bomber attacked a Shi'ite mosque in Baghdad, killing 17 worshippers, while a triple car bombing in the holy city of Karbala killed 16.
Police said the bomber blew himself up among the worshippers as they were leaving the Al-Khairat Mosque in central Baghdad after noon prayers.
In Karbala, three separate car bombs went off simultaneously, killing at least 16 and injuring more than 40 others.
The attacks came a day after a suicide bomber targeted a Shi'ite mosque in Baghdad's western Harithiya neighborhood, killing at least 22 people.
There were no immediate claims of responsibility for the attacks.
Islamic State militants have recently claimed several other large bombings in Iraq, particularly in Shi'ite areas.