Iraq has imposed tough security measures as part of a four-day public holiday leading into a constitutional referendum on Saturday.
Coalition forces helped set up checkpoints and concrete security barriers near polling stations across the country. Officials also announced a curfew and plans to close the border and ban vehicles from roads on Friday.
The measures are aimed at preventing violence by insurgents who have vowed to disrupt the vote. Thursday, two Iraqi policemen died in northern Iraq, and roadside bombs elsewhere killed killed two civilians and an American soldier.
About 15-and-a-half million Iraqis are eligible to vote, including some detainees who began casting early ballots Thursday.
Iraqi officials approved last-minute changes to the draft this week, in an effort to win support from Sunni Arabs, who oppose it. But many Sunni groups say they will still vote "no."