Among those killed were six who died in a mass assassination south of Baghdad, in scenes reminiscent of the worst of Iraq's 2006-07 sectarian conflict in which tens of thousands were killed.
The surge in violence has left more than 2,400 people dead so far this year.
It is principally driven by anger in the Sunni Arab minority over alleged mistreatment at the hands of the Shiite-led authorities, as well as spillover from the war in neighbouring Syria.
Six Sunni Arabs were killed by militants, security and medical officials said, but accounts differed as to how they died.
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Two officials reported a family of six were stabbed to death, while others said six Sunni men were taken from various houses in the town and shot dead.
Attacks also struck in the restive northern provinces of Kirkuk, Nineveh and Salaheddin, leaving four people dead, while six militants were also killed.
But with parliamentary elections looming at the end of this month, Prime Minister Nuri al-Maliki and other Shiite leaders have been loath to be seen to compromise.
Near-daily bloodshed is part of a long list of voter concerns that also include lengthy power cuts, poor wastewater treatment, rampant corruption and high unemployment.