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.
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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.