A suicide bomber killed at least six Iraqi civilians in an attack on a checkpoint in the Sunni Arab town of Fallujah, Iraqi police said.
Captain Mohammed Hussain said the suicide bomber targeted a joint Iraqi and US military checkpoint in the Al-Julan neighbourhood of Fallujah, 50 kilometres west of the capital Baghdad.
"The victims were civilians," he said.
There was no immediate reaction from the US military.
Fallujah in Anbar province has been relatively calm since the US policy began of recruiting former insurgents into so-called Awakening fronts against al-Qaeda jihadists.
Attacks in the region declined drastically in the past year, according to the US military which credits Awakening groups with playing a key role in reducing the violence.