The shootings and bombings, which also wounded dozens more, came with campaigning in full swing for the April 30 election and with violence at its highest level since 2008.
The unrest has been principally driven by anger in the Sunni Arab community over alleged mistreatment at the hands of the Shiite-led government and security forces, as well as a spillover from the civil war in neighbouring Syria.
Apart from the capital, today's violence struck in predominantly Sunni areas of Nineveh, Salaheddin and Kirkuk provinces to the north, and in Anbar to the west, while security forces engaged in a firefight with insurgents south of Baghdad, security and medical officials said.
Elsewhere, a suicide bomber killed an army captain and his son when he blew himself up on the doorstep of the officer's home in Baiji, while bombings in Baghdad and in the northern provinces killed six others.
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Gunmen also shot dead two anti-Al-Qaeda militiamen in Salaheddin's capital Tikrit.
In conflict-hit Anbar, army shelling of the militant-held town of Fallujah killed two people, while clashes between security forces and anti-government fighters in provincial capital Ramadi left two policemen dead.
While security forces have managed to wrest back control of most of Ramadi, Fallujah has been out of government control for about three months.
Militants also destroyed a bridge just north of the capital by setting off several bombs along it.
More than 2,300 people have been killed in Iraq so far this year, according to an AFP tally.