In Baghdad, bombs went off as the sun rose in the Shiite neighborhoods of Sadr City and Khadimiyah, The Guardian reported. They killed 24 people.
Those bombings and the suicide attack on pilgrims walking from Nasiriyah to the holy city of Karbala are believed to be the work of the Islamic State of Iraq, a Sunni group inspired by al-Qaida, The Guardian said. The group took responsibility for another series of anti-Shiite bombings in December.
The suicide bomber set off an explosive vest as a soldier attempted to stop him, officials said. The blast wounded at least 100 people.
The pilgrims were preparing for Arbaeen, a holy day which marks the end of a 40-day mourning period for Imam Hussein, a grandson of the Prophet Mohammed killed in a 7th century battle.
The first Sadr City bomb went off in an area where day laborers had gathered, officials said. Two other bombs exploded as rescuers worked to get wounded to a hospital, The New York Times reported.
About an hour later, two car bombs went off in the largely Shiite neighborhood of Kadhimiya, killing 15 people and wounding 31, security officials said.
Iraqi leaders have expressed concern about an increase in violence after the U.S. military withdrew from Iraq. The country has been in political upheaval as the Shiite government of Prime Minister Nouri al-Maliki accused the country's Sunni vice president, Tariq al-Hashimi, of running a death squad. Sunni and Kurdish politicians have boycotted parliamentary sessions, accusing Maliki of trying to consolidate his power.