Attackers struck the Sahwa checkpoint in Khan Beni Saad, 40 kilometres (25 miles) north of Baghdad in Diyala province, while some of the Sunni Arab militiamen were asleep, according to an official in the security command centre in provincial capital Baquba.
The shooting killed five Sahwa militiamen, a doctor at Baquba hospital said. The security official confirmed the toll. Both spoke on condition of anonymity. The Sahwa are made up of Sunni tribesmen who joined forces with the US military against Al-Qaeda from late 2006, helping turn the tide of the insurgency.
Violence in Iraq is down from its peak in 2006 and 2007, but attacks remain common. A total of 187 people died in violence in November, according to official figures.