A suicide bomber hit a mosque in Baghdad as Shiite worshippers left after noon prayers, killing 17 people, while a triple car bombing in the holy city of Karbala killed 16.
Iraq has been plunged into its worst crisis since the US troops left at the end of 2011 in the wake of the blitz by the Islamic State militants this summer.
The extremists group captured large chunks of land in western and northern Iraq, carving out a proto-state on the territory it controls between Syria and Iraq and imposing its own harsh interpretation of Islamic law, or Shariah.
Since August, US warplanes have been carrying out airstrikes against the group as Iraqi and Kurdish security forces work to retake territory it has seized. In Baghdad, the bomber blew himself up among Shiite worshippers as they were leaving a mosque in a commercial area in the city centre after midday prayers today, killing at least 17 people and wounding 28, a police officer said.
In Karbala, three separate car bombs went off simultaneously, killing at least 16 people and wounding 41, another police officer said. The city, about 90 kilometres south of Baghdad, is home to the tombs of two most revered Shiite imams and the site of year-round pilgrimages. The explosives-laden cars were parked in commercial areas and parking lots near government offices, the officer added.
Medical officials confirmed the casualty figures. All officials spoke on condition of anonymity as they were not authorised to talk to media. The attacks in Baghdad and Karbala came a day after a suicide bombing targeted another Shiite mosque in the Iraqi capital, in the western Harithiya neighbourhood, killing 28 people.
No one immediately claimed responsibility for the latest attacks but they bore the hallmarks of the al-Qaida-breakaway Islamic State group, which has recently claimed several other large bombings in Baghdad and elsewhere, particularly in Shiite areas.