The American Army announced on Friday start of a new wide-scale military operation west of the Iraqi capital and said the action was aimed at locating and wiping out insurgents' hideouts. The army said in a statement that the assault was spearheaded with advance of American and Iraqi troops, adding that 21 suspected terrorists were arrested and large caches of arms were seized in the operation.In the Iraqi capital, gunmen attacked a police patrol in Al-Mansour district, killing three policemen and wounding another, a security source said. The gunmen spead off in a car. Suspects were also apprehended in a mop-up operation in regions around the northern city of Kirkuk.