The gunmen in military uniforms broke into a house in Mahmudiyah, 30 kilometres (18 miles) south of Baghdad, and shot dead the parents and three children, an interior ministry official said.
A medical source at the hospital in Mahmudiyah said it had received the bodies of eight members of a Shiite family -- a man, a woman and six children aged between four and 14 years old. All had been shot in the head.
Mahmudiyah is a mixed Sunni-Shiite town that was formerly a Sunni insurgent stronghold.
Gunmen also attacked a house in Saadiyah near Khanaqin, 150 kilometres (95 miles) northeast of Baghdad, killing Mohsen Hassan, an Iraqi communist party member, and his wife, Shahad Ahmed, a police lieutenant colonel and a Baquba hospital doctor said.
The Iraqi communist party was once of one the strongest in the region but was decimated by now-executed dictator Saddam Hussein.
The shootings come just two days after a wave of bomb and gun attacks killed 72 people and wounded more than 250 across Iraq, the country`s deadliest day in almost 10 months.
Violence across Iraq has declined dramatically since the 2006-2007 peak but attacks remain common, especially in Baghdad. A total of 132 Iraqis were killed in May, official figures show. (*)
Editor: Kunto Wibisono
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