Gunmen attacked a checkpoint on Friday near Samarra, north of Baghdad, killing five anti-Qaeda fighters and wounding two others, a police lieutenant colonel and a doctor said.
Four of the attackers were also killed, the police officer said.
The attack comes a day after gunmen killed seven Sahwa fighters and wounded one other in two separate attacks -- one south of the Iraqi capital, and the other west of Kirkuk in the north.
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.
Violence in Iraq has decreased from its peak in 2006 and 2007.
But even 10 years after the US-led invasion of the country attacks remain common, killing 220 people last month, according to an AFP tally based on security and medical sources.