Baghdad (CNN) -- 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.
The gunmen stormed a house in the al-Thuraa neighborhood and then fled after the killings, 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.
In other violence Sunday, four Katyusha rockets hit different areas of Baghdad, including one in the heavily fortified Green Zone where Iraqi government and diplomatic buildings are located, according to information ministry officials.
A total of 13 people were wounded in the rocket attacks, though ministry officials had no immediate information on any possible casualties from the rocket that landed in the Green Zone.
Separately, a roadside bomb exploded outside Iraq's National Theatre in central Baghdad, wounding three people, and a mortar round damaged a house in central Baghdad but caused no casualties, the information ministry officials said.