Updated

U.S. forces and Iraqi police raided an area west of Baghdad (search) on Saturday and arrested 11 people suspected of links to insurgents, witnesses said following the bloodiest day of attacks against American forces in a month.

Meanwhile, efforts to get oil from the large fields of northern Iraq hit a new hitch Saturday. The flow of oil through the main pipeline from the north to Turkey (search) resumed for the first time since August, but ran for only two hours before a leak was discovered and the pipeline had to be shut down again.

Eight men and three women were taken into custody during the raids, which began before dawn around the flashpoint town of Khaldiyah in the "Sunni Triangle (search)" west of Baghdad, according to local residents. The Sunni Muslim (search) areas north and west of Baghdad have been the scene of most attacks against American troops.

There was no comment from U.S. authorities about the raids, which took place one day after U.S. forces suffered four deaths in two separate attacks — the bloodiest daily death toll since Sept. 18, when three soldiers were killed in an ambush in Tikrit. Nearly 20 soldiers were reported wounded in several clashes across the country.

With the latest deaths, the number of U.S. soldiers who have died by hostile fire since President Bush declared an end to major combat on May 1 has climbed to 101. A total of 211 soldiers have been killed in fighting and attacks in Iraq since the war began.

The ongoing bloodshed has raised questions about U.S. stewardship of Iraq, especially since the United States has been unable to find any weapons of mass destruction, whose alleged presence in Saddam Hussein's arsenal was cited as the major justification for the war.

During a visit Friday to U.S. troops in Tikrit, Lt. Gen. Thomas F. Metz, commander of the Army's 3rd Corps, told reporters that American troops would be in Iraq for another troop rotation or even two. At current pace of a turnover of troops every year, that could mean U.S. forces would be in Iraq until 2006.

The four deaths suffered Friday included Lt. Col. Kim S. Orlando, 43, the highest-ranking Army officer killed by hostile fire since the Iraq war started on March 20, said Maj. Steve Stover, an Army spokesman at the Pentagon. Orlando was commander of the 716th Military Police Battalion.

Three of the soldiers, including Orlando, were killed after a joint U.S.-Iraqi patrol confronted gunmen outside the headquarters of a Shiite Muslim cleric in the holy city of Karbala, 50 miles south of Baghdad. Ten Iraqis were also killed, including two Iraqi policemen, U.S. and Iraqi sources said.

Another American soldier was killed and two were wounded by a roadside bomb Friday near Baghdad, and nine U.S. troops were wounded in a roadside bombing in the northern city of Mosul.

The other two killed in the clash in Karbala were Staff Sgt. Joseph P. Bellavia, 28, of Wakefield, Mass.; and Cpl. Sean R. Grilley, 24, of San Bernardino, Calif., according to a statement by Fort Campbell, Ky. The name of the soldier killed in the Baghdad area was not released.

Elsewhere, Dutch marines clearing munitions in the southern al-Muthana province have called in British and American weapons inspectors after finding "a few dozen suspect shells," a Defense Ministry spokesman in the Netherlands said Saturday. The 130-mm artillery shells found Oct. 8 showed "several indications of some kind of chemical reaction," a Dutch spokesman said, although he added they could be regular munitions discolored by the heat and sun.

The bloody battle in Karbala took place intermittently over a 12-hour period starting about midnight on Thursday. It underscores the dangers of trying to disarm militias maintained by Shiite clerics who wield considerable influence in Iraq's largest religious group. The U.S.-led coalition has banned private militias and is committed to disarming them.

Pentagon officials said they were investigating how the shooting began. Iraqis insisted the Americans fired first.

Most of the violence directed against Americans has come from the minority Sunni Muslim community, which formed the base of Saddam's regime. The spread of anti-American violence into the Shiite community, which comprises about 60 percent of Iraq's 25 million people, would present a grave challenge to the United States as it strives to restore order and establish a functioning democracy.