The bombings in Baghdad and the north and west raise serious concerns about the security forces' ability to protect people during Wednesday's general election, when more than 20 million Iraqis are eligible to vote.
They come amid a protracted surge in violence and fears the country is edging towards all-out conflict.
Seven attackers wearing suicide belts hit polling stations in Baghdad and cities north of the capital, while roadside bombs struck military convoys and targeted journalists covering the polling.
Five members of the security forces were killed by another suicide bomber at a polling station in the city's north.
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Attacks elsewhere killed 15 members of the security forces, officials said.
In the main northern city of Mosul, six Iraqi journalists were wounded as a bomb exploded while they were in a military vehicle to cover the vote.
The blasts shattered an early morning calm as soldiers and policemen queued outside polling stations amid tight security, before leaving with the traditional purple ink-stained finger indicating they had voted.
Govt officials did not publicly comment on the attacks.
Prime Minister Nuri al-Maliki, lambasted by critics for allegedly consolidating power and targeting minority groups amid worsening security, is seeking a third term with Iraqis frustrated over poor basic services, rampant corruption and high unemployment.
The month-long campaign has seen Baghdad and other cities plastered with posters and decked out in bunting, as candidates have taken to the streets, staged loud rallies and challenged each other in angry debates.