The car bomb in the Mashtal area of east Baghdad also wounded 23 people, interior ministry spokesman Brigadier General Saad Maan told AFP.
In Sinjar, west of the northern city of Mosul, militants shot dead a mother and three sons, all members of the Yazidi religious sect, at their home.
And a bomb near a house in Baquba, also north of Baghdad, killed two members of the same family and wounded five, while gunmen killed one Sahwa anti-Al-Qaeda fighter and wounded another in an attack on a checkpoint near the city.
Violence in Iraq has reached a level not seen since 2008, when the country was just emerging from a brutal sectarian conflict.
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The surge in unrest, which has included sectarian attacks, has raised fears of a relapse into the intense bloodshed that peaked in 2006-2007 and killed tens of thousands of people.
Analysts say the Shiite-led government's failure to address the grievances of Iraq's Sunni Arab minority -- which complains of political exclusion and abuses by security forces -- has driven the surge in unrest this year.
The authorities have made some concessions aimed at placating the protesters and Sunnis in general, such as freeing prisoners and raising the salaries of Sunni anti-Al-Qaeda fighters, but the underlying issues remain unaddressed.
With the latest attacks, more than 420 people have been killed so far this month, and over 5,100 since the beginning of the year, according to AFP figures based on security and medical sources.