North of Baghdad, gunmen dragged 17 people out of their homes and killed them early on Wednesday, police said.
Police said the gunmen rounded up their victims in the middle of the night and shot them outside their houses in Taji.
Sectarian killings have raised fears of civil war in Iraq, where insurgents are waging a campaign of suicide bombings and shootings in a bid to topple the U.S.-backed government, reports Reuters.
According to an interior ministry official quoted by AFP news agency, the attackers in Taji, 15km (nine miles) north of Baghdad, arrived in the town on "military vehicles" and were dressed as soldiers.
They "arrested several [people] before assembling them on a public square and shooting them", said the unnamed official, informs BBC.