Three Shiite family members, including a woman, were fatally shot by gunmen wearing police uniforms in southwestern Baghdad on Sunday morning, Iraq's interior ministry said.
Gunmen stormed a house in the al-Thuraa neighborhood and fled, ministry officials said. Iraqi security forces are investigating.
In the past few months, gunmen have stormed houses across the country in similar incidents and fatally shot family members.
Interior ministry officials have attributed these killings to either the sectarian violence between Sunnis and Shiites or tribal retaliations.
Overall, violence in Iraq has dropped drastically since the peak of sectarian violence between 2005 and 2007, but mortar attacks, bombs and assassinations are still common.