U.S. military officials say American troops are helping Iraqi forces patrol the northern town of Balad to stop a wave of sectarian attacks.
Iraqi officials say at least 74 Sunni Arabs have been killed in retaliation for the slaying of 19 Shi'ite Muslim workers on Friday.
U.S. military officials said American troops had detained two Iraqi police officers allegedly linked to the killing of the Shi'ite workers.
Local officials said militia linked to radical Shi'ite cleric Moqtada al-Sadr were involved in the attacks. They say many Sunni families have fled to the nearby city of Duluiyah to escape the violence.
Meanwhile, an interior ministry spokesman, Brigadier General Abdul Kharim Khalaf, said at least two police commanders have been reassigned as part of a restructuring plan. He added that more than 3,000 police officers have been removed from duty, including some for breaking the law.
Critics have repeatedly accused the interior ministry and its police force of having links to Shi'ite militias and alleged death squads.
In the southern city of Basra, police said gunmen killed four students and a female doctor.
A Kurdish politician, Fatah Hurki of the Patriotic Union of Kurdistan, was shot dead in the northern city of Mosul.
And a mortar shell landed in a Baghdad square, killing at least two people and wounding three others.
Some information for this report was provided by AFP, AP and Reuters.