Most of the attacks in Baghdad targeted Shiite areas, police told CNN. Al-Qaida in Iraq, composed of Sunni extremists, claimed responsibility for many of the attacks that occurred in recent months.
Two of the bombings targeted a checkpoint near Baghdad's international airport, while attacks elsewhere struck police checkpoints, Shiite neighborhoods and political offices.
In northern Iraq, three car bombs detonated separately in Tuz-Khurmato, a local police official told China's state-run news agency Xinhua.
In Kirkuk, three car bombs went off throughout the city, officials said.
Elsewhere, two car bombs went off in Nassriyah, a suicide bomber detonated his vest at a checkpoint near Dowr and two more cars exploded in Babil governate, Xinhua said.
The latest violence occurred as Iraq prepares for provincial elections scheduled for Saturday.