U.S. Marines patrol the city of Kubaysah in western Iraq

The U.S. military has launched a new operation in western Iraq aimed at rooting-out foreign fighters and insurgents in a bid to boost security ahead of the October 15 referendum on the country's new constitution.

The U.S. military says about 1,000 marines, soldiers and sailors launched the offensive early Saturday in the town of Sadah, near Qaim, about 12 kilometers from the Syrian border.

Meanwhile, in the northern city of Kirkuk, police say a roadside bomb exploded near one of their patrols, killing at least three officers.

Also Saturday, the U.S. military reports that two American soldiers were killed in separate incidents in Baghdad and Bayji. Also a Danish soldier was killed and two were wounded in the southern city of Basra, where about 500 Danish soldiers are based.