Senior Sunni Muslim clerics in Iraq have urged their followers to join the country's security forces.
Iraqi police are regularly targeted by insurgents
Sunnis form the bulk of the anti-US insurgency, which frequently attacks the police and army.
A Iraqi government spokesman said the call on Sunnis to participate in the security forces was a welcome change.
Later, four policemen and a passing driver were killed by a car bomb in the so-called Sunni triangle, a stronghold of the insurgency.
The bomb in Khan Bani Saad, 20km (12 miles) north-east of Baghdad, exploded as police were checking it.
In another incident, a US marine was shot dead while conducting a security operation in the western city of Ramadi, the US military says.
Until recently, many Sunni clerics had branded the security forces as US collaborators.
The army and police are largely dominated by Shias and Kurds.
Ahmed Abdul Ghafour al-Samarrai of the Association of Muslim Scholars said Sunni membership was necessary to prevent the forces falling into "the hands of those who have caused chaos, destruction and violated the sanctities".
However, the group consisting of 64 clerics and scholars also told Sunnis not to help foreign troops against their own countrymen.
The change of heart appears to have been prompted by January's elections when millions of Iraqis defied the insurgents to cast their ballots, says the BBC's Caroline Hawley in Baghdad.
Sunnis mostly boycotted the vote but have since been rethinking their role in Iraq's political future.
On Friday, Iraqi lawmakers held last-minute meetings on who would be the parliament speaker of the newly elected national assembly.
However, they remain deadlocked on which Sunni candidate should take the job, the Associated Press news agency reports.