In the Dura area of southern Baghdad, gunmen armed with silenced weapons shot dead a father, mother, four sons and the wife of one of them at their home, the officials said.
The father was a member of the Sahwa anti-Al-Qaeda militia, who joined forces with the United States from late 2006 and are frequently targeted by Sunni militants, who view them as traitors.
In the Mansur area of west Baghdad, a lawyer was killed by a magnetic "sticky bomb" attached to his car.
Shiites are also often targeted by Sunni militants, who consider them apostates.
More than 580 people have now been killed this month, and 5,300 since the beginning of the year, according to AFP figures based on security and medical sources.
A study released this month by academics based in the United States, Canada and Iraq said nearly half a million people have died from war-related causes in Iraq since the US-led invasion of 2003.