U.S. forces have arrested hundreds of Iraqis in a bid to end guerrilla attacks on U.S. troops. The military operation is the biggest in Iraq since the war ended.

U.S. military officials say thousands of ground troops, backed by warplanes, attack helicopters and river patrols, are pushing through a 50 square kilometer area north of Baghdad in search of weapons and fighters.

The area, dominated by Sunni Muslims, is known as the Sunni triangle, and was deposed Iraqi leader Saddam Hussein's control base. It has been the center of a recent surge of attacks, in which at least 10 American soldiers have been killed and dozens wounded during the past two weeks.

American officials say they have intelligence that senior Baath Party officials are hiding in the Tigris River region.

The series of U.S. raids, code named Operation Peninsula Strike, is meant to capture Baath Party loyalists planning and carrying out attacks on U.S.-led coalition troops.

So far, U.S. troops have detained about 400 Iraqis for questioning. They say prisoners found not to be hostile will be released. But they say that, if suspects are believed to be dangerous and a possible cause of problems for the Iraqis or coalition forces, they will be held for further questioning.

Iraqi civilians bitterly complain that the operation is excessive, with women and children also being handcuffed. But U.S. officials deny the charges. They insist the operation is part of a continuing effort to secure peace in Iraq.

Meanwhile, U.S.-led coalition forces warned foreign diplomats in Baghdad that they remain in Iraq at their own risk. They say they will be able to deploy troops or guards only for their own safety, with prior coalition authorization.

Some 30 diplomatic missions have been set up in the Iraqi capital, despite the coalition's refusal to grant diplomatic immunity to representatives of foreign governments.