Several attacks have killed at least 13 people across Iraq.
In the town of Khalis, 80 kilometers north of Baghdad, a suicide bomber struck a group of Iraqi Shi'ite pilgrims, killing six and wounding 16.
Outside the city of Samarra, 95 kilometers north of Baghdad, gunmen opened fire on a bus carrying Pakistani Shi'ite pilgrims, killing three Pakistanis and two Iraqis, and wounding 12.
In the western city of Ramadi, a suicide car bomber killed two police officers and wounded five.
Hundreds of thousands of Shi'a make pilgrimages to the holy city of Karbala during the 40-day annual commemoration marking the death of the Prophet Muhammad's grandson, Imam Hussein.
They are often the target of Sunni extremists.
According to the United Nations, more than 8,000 people have been killed in Iraq in renewed sectarian violence this year.
Based on reporting by AP and AFP