The official said the attackers entered the family home in Bayaa neighbourhood early on Sunday and murdered three of the family, including a woman, before making their escape.
There was no immediate indication of the motive for the attack.
Violence in Iraq is down markedly from its peak in 2006 and 2007 but attacks remain common.
A total of 211 people died in violence last month, according to official figures.
(Uu.M014)
Editor: Priyambodo RH
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