The offensive, called Operation Swarmer, involves 50 helicopters, making it the biggest air assault since the U.S.-led invasion of Iraq in 2003.
A U.S. military spokesman said U.S.-led forces are searching a 256-square-kilometer area of desert country for guerrillas, and that no casualties have been reported by American or Iraqi forces.
He said 50 people have been detained, of which 30 remain in custody. Stolen weapons and explosives have also been seized.
(Reuters)