U.S. helicopter gunships backed an artillery bombardment aimed at insurgents in southwest Baghdad (searchon Wednesday, as troops raided homes and arrested a Sunni (search) sheik said to be close to the most wanted man in Iraq.

In northern Iraq, a car bomb exploded outside the office of the Interior Ministry in Irbil (search), near Kirkuk (search), and several people were killed or injured, said Kamil Kerkukly, an official of the Kurdistan Democratic Party.

Irbil houses the Kurdish parliament. Under U.S.-led aerial protection, Iraqi Kurds, ethnically distinct from the majority Arabs, have ruled an autonomous Switzerland-sized stretch of northern Iraq since the end of the Gulf War more than a decade ago.

Also Wednesday, a minibus detonated a roadside bomb in a Baghdad traffic tunnel, killing one civilian and wounding two others, Iraqi police said. The bomb exploded in the Shurta tunnel around noon, when roads fill as residents go home for lunch.

In Baghdad, residents said explosions from the U.S. bombardment were heard from before midnight until about 2 a.m. Maj. John Frisbie of the 1st Armored Division told The Associated Press that the barrage was aimed at several targets.

He would not elaborate on the targets but said 2nd Brigade made no arrests. Wednesday's barrage could have been a show of force as the military steps up security against threats of attacks over the Christmas holiday by Baghdad's 14 identified guerrilla cells.

Frisbie indicated the military was still acting on information gleaned from the Dec. 13 capture of Saddam Hussein, and residents were also giving information.

"We continue to gain intelligence from the neighborhoods here and the residents of Baghdad who are seemingly frustrated at these continued (rebel) attacks," Frisbie said.

In Washington, Gen. Richard Myers, chairman of the Joint Chiefs of Staff, said Tuesday that information resulting from Saddam's capture led to arrests of 50 former regime leaders the day before. There was a similar surge of information after Saddam's sons, Odai and Qusai, were killed in July, he told reporters at the Pentagon on Tuesday.

"The same phenomenon that happened after his sons were killed is happening again, which is a good sign and it probably tells you the role that fear plays in people's minds," Myers said.

On of the latest targets was Ghazi Hanash, leader of al-Ta'ee tribe based around the northern city of Mosul. He is said to be close to former Vice President Izzat Ibrahim al-Douri, who U.S. commanders say could be organizing the anti-American resistance.

Al-Douri -- No. 6 on the U.S. list of the 55 most-wanted Iraqis -- is the most senior official of 13 who have escaped custody.

Hanash was arrested at his apartment in Baghdad along with a son and two aides, a cousin, Ghassan Hamadi, said from the Sheik's residence in Mosul.

Before dawn Tuesday, Hamadi said, U.S. troops raided the Mosul house but found only frightened women, who called for help from a cousin living nearby. As the cousin, Mohammed Ajeel, approached the house, he was shot and killed by the Americans, Hamadi said.

It was not immediately possible to get military comment on his report, but U.S. troops have reported the deaths of at least three Iraqis in such attacks in the past week.

U.S. soldiers have arrested dozens of suspected rebels in the past 10 days, including several believed to be recruiting ex-soldiers to attack the U.S. military, their allies and Iraqis working with the U.S.-led occupation.

Also Tuesday, U.S. Army divers found the body of an American soldier in the Tigris river after he went missing two weeks ago. The soldier had jumped into the river on Dec. 10 to save another soldier who fell overboard during a boat patrol. The man who fell also drowned, and his body was discovered the day after the accident.