Updated

U.S. forces attacked dozens of suspected guerrilla hideouts in Saddam Hussein's hometown, killing six alleged insurgents as they pressed their search Monday for a former Saddam deputy believed to be orchestrating attacks on Americans.

Military spokesman Brig. Gen. Mark Kimmitt said the U.S.-led coalition was intensifying its search for Izzat Ibrahim al-Douri, No. 6 on the most-wanted list of 55 Iraqis and former vice chairman of Saddam's Revolutionary Command Council.

"We are getting intelligence now that he is directly involved in the killing of coalition soldiers," Kimmitt said.

Also Monday, an Iraqi militant group called Muhammad's Army (search) claimed responsibility for the downing of a U.S. helicopter on Nov. 2 that killed 16 soldiers. The group warned that U.S. forces would face more attacks if they did not leave Iraq in 15 days. There was no way to independently verify the claims.

In a videotape broadcast by the Lebanese Al Hayat-LBC satellite channel, Muhammad's Army also claimed responsibility for the assassination of a member of the U.S.-backed Iraq government council and another attack on American troops.

The group is seeking to return Saddam to power and consists of several hundred former Iraqi intelligence and security services. A group with this name is one of several that claimed responsibility for the Aug. 19 bombing of U.N. headquarters in Baghdad.

Kimmitt said coalition forces had captured 99 suspected insurgents, including a former general in Saddam's elite Republican Guard, during 1,729 patrols and 25 raids conducted over the past 24 hours.

Last month, a senior U.S. defense official said al-Douri was believed to be helping coordinate attacks on American forces with members of Ansar al-Islam, an Al Qaeda-linked terrorist group in the north. The information about al-Douri's role came from two captured members of Ansar al-Islam (search), said the official, who spoke on condition of anonymity.

Al-Douri was one of Saddam's few longtime confidants and his daughter was married to Saddam's son, Odai, who was killed in a raid by U.S. forces in July.

Shortly before the U.S.-led invasion began March 20, Saddam announced a reorganization of Iraq's defenses, naming his son Qusai and other trusted aides to command each of four sectors across the country. Al-Douri was named commander for the northern sector.

Tikrit, about 120 miles north of Baghdad, is part of a region north and west of Baghdad dominated by Sunni Muslims and regarded as a hotbed of anti-American sentiment.

During Monday's raids, U.S. forces fired a satellite-guided missile carrying a 500-pound warhead at a suspected insurgent sanctuary 10 miles south of Tikrit (search) — the second use in as many days of the powerful weapon amid a U.S. drive to intimidate the resistance.

Hundreds of U.S. troops in tanks and assault vehicles marched through crowded downtown Tikrit Monday in a show of force intended to deliver a stern warning.

"They need to understand that it's more than just Humvees that will be used against the resistance and we will crush the resistance," said Lt. Col. Steven Russell, a battalion commander in the 4th Infantry Division.

U.S. forces carried out dozens of attacks from Sunday night to early Monday, destroying 15 suspected safehouses, three training camps and 14 mortar firing points, said Lt. Col. William MacDonald, a spokesman of the 4th Infantry Division.

Six suspected Saddam loyalists were killed and 21 arrested, he said.

"Clearly, we're sending the message that we do have the ability to run operations across a wide area," said MacDonald. "We have overwhelming combat power that we will utilize in order to go after groups and individuals who have been conducting anti-coalition activities."