Five US soldiers have been killed by a roadside bomb on in Ramadi, west of Baghdad, the US military said in a statement.
The statement gave no details beyond saying the soldiers were assigned to the 2nd Marine Division.
The soldiers’ deaths came as some 10 million Iraqis headed to the polls to vote on a referendum on a draft constitution.
Although there were reports of heavy fighting in Ramadi, the capital Baghdad witnessed the lowest level of violence in months.
In Falluja 50km west of Baghdad, two Iraqi soldiers were killed and three wounded when armed men hurled grenades in a market, police officer Sami Muhammed said on Sunday.
US forces killed 10 fighters insurgents in Karabila, 300km west of Baghdad, the US military said also on Sunday.