Five Sunni tribal leaders opposed to al-Qaeda have been killed after a suicide bomber drove a minivan packed with explosives into a house north of Baghdad.
The men were meeting in Jurf al-Milih, near Taji, about 20km north of the Iraqi capital, to discuss joining US and Iraqi forces in fighting al-Qaeda.
A police source said another 12 people were wounded in Sunday's attack and the death toll could rise.
An Iraqi army source said the tribal chiefs were meeting after talks with local Shia leaders were held in Taji on Friday under the protection of US forces.
Special units
US military commanders have been trying to expand their plan, first used in the violent western province of Anbar, of recruiting local Sunnis who are tired of al-Qaeda violence into special provincial police units.
Al-Qaeda is blamed for stoking sectarian hatred and violence between majority Shias and minority Sunni Arabs who were dominant under Saddam Hussein, the former Iraqi leader.
The US military began a security crackdown in Baghdad five months ago which initially helped bring down the number of sectarian murders but which also pushed al-Qaeda fighters out of the capital and into surrounding areas.
US and Iraqi forces later launched another big operation in the middle of June coinciding with the arrival of the last of 28,000 extra US troops in Iraq.