Unidentified gunmen killed a former member of Iraq's Sahwa militia and five members of his family before dawn on Thursday in the fourth attack on the anti-Qaeda force in a week, police said.
The gunmen laid siege to the home of Qudair Hamed Saud in the village of Fielat outside the former insurgent bastion of Fallujah and stormed it after an hour-long firefight, police Captain Anas Saadun said.
Those killed alongside Saud were his brother, three women and a child.
Medics in the town west of the capital Baghdad confirmed the deaths.
There have been repeated attacks on the Sahwa (Awakening) militia, also known as the Sons of Iraq, which is largely made up of Sunni Arab tribesmen and former insurgents who turned against Al-Qaeda.
Most attacks have been blamed on jihadists angry that the militiamen had switched sides and made common cause with the US military and the Shiite-led government in Baghdad.
On Monday, a Sahwa member and his wife were killed when a bomb attached to their car exploded several kilometres (miles) north of Baquba, capital of Diyala province -- an Al-Qaeda stronghold north of Baghdad.
Last Friday, three Sahwa members were killed in the northern oil hub of Kirkuk when a grenade exploded near their checkpoint, police said.
And last Thursday, a suicide bomber killed three Sahwa members and two soldiers in west Baghdad, security spokesman Major General Qassim Atta said.