A police official said the deadliest attack took place at night, when gunmen ambushed a minibus carrying off-duty soldiers near the town of Suleiman Beg, killing eight and wounding four others.
Security forces launched a manhunt in the town, which is about 150 kilometers north of Baghdad.
Earlier, a car bomb explosion in a town just north of Baghdad killed two people.
Another car bomb exploded in a residential area in the city of Hillah, killing three people and wounding eight others. Hillah is about 95 kilometers south of Baghdad.
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Today's attacks came a day after the announcement of results from national elections held April 30, in which a coalition led by Iraqi Prime Minister Nouri al-Maliki emerged in first place.
Violence has surged in Iraq since last year, with the country weathering its deadliest bout of unrest since the dark days of 2006 and 2007, when sectarian attacks including near-daily bombings killed tens of thousands of people.
United Nations figures show that violence last year in Iraq killed 8,868 people.