Iraq Offensive

Dozens of suspected insurgents are being detained after the first day of "Operation Swarmer," a major U.S. Iraqi military offensive aimed at rooting out troublemakers around the city of Samarra, north of Baghdad.

Fifty helicopters carrying U.S. and Iraqi troops swarmed in Thursday in what the American military calls the largest air assault in nearly three years.

An Iraqi commander describes the targets as "a bunch of strange criminals who came from outside the country" and "a bunch of Iraqi criminals who help them."

Samarra is where a mosque attack last month sparked a wave of sectarian killings.

And the area has been infested with insurgent roadblocks and ambushes.

One Iraqi official says gunmen have been "killing and kidnapping policemen, soldiers and civilians."