Gunmen in military uniforms attacked the house of an Iraqi anti-Qaeda militia leader north of Baghdad on Friday, killing him and three of his sons, a police officer and a doctor said.
The gunmen bound their hands and killed Khalil al-Ajili and one of his sons in the house near Baquba, a police lieutenant colonel said, adding the other two tried to escape but were killed in a nearby field.
A doctor from Baquba General Hospital confirmed the toll.
With the latest attack, 17 members of the Sahwa anti-Qaeda militia forces have been killed in violence this month.
The Sahwa are made up of Sunni Arab tribesmen who joined forces with the US military against Al-Qaeda from late 2006, helping turn the tide against the insurgency.
The Iraqi government announced at the end of January that about 41,000 Sahwa fighters are to receive 500,000 Iraqi dinars ($415) a month, up from 300,000 dinars ($250).
An increase in wages for the Sahwa, as well as their incorporation into the security forces and civil service, has long been a demand of Iraq's Sunni community.