Iraqi officials say gunmen shot dead 22 Shi'ite pilgrims in an ambush in a remote desert area of western Anbar province.

The pilgrims were travelling from the southern Iraqi city of Karbala Monday when their bus was stopped at a fake checkpoint set up by the gunmen.

The assailants then ordered all the women and children off the bus, drove a few kilometers from the main highway and killed all the men.

Officials gave conflicting accounts as to whether the pilgrims were headed to their destination — a shrine in neighboring Syria — or returning.

Sprawling Anbar province was the center of a Sunni Islamist insurgency after the U.S. invaded Iraq. Many insurgents have continued to launch attacks there while posing as Iraqi soldiers.