March 31 (Bloomberg) -- Four U.S. contractors riding in two vehicles were attacked and killed west of Baghdad in what White House spokesman Scott McClellan said were ``horrific, despicable'' assaults that ended with Iraqis mutilating the corpses.

In a separate incident, five U.S. soldiers were killed when a bomb went off under their vehicle.

Coalition spokesman Dan Senor said in Baghdad that the bodies of the contractors, who weren't identified, were pulled from the vehicles in Fallujah, a town of entrenched resistance to the occupation. Senor also referred to television images that showed Iraqis dragging them through the streets.

Photographs by Agence France-Presse showed Iraqis gathered around a charred body and near sport-utility vehicles that were consumed by flames. An Associated Press photo showed cheering residents on a bridge, where other remains were hung from the superstructure.

The killers are ``trying to shake our will,'' McClellan said in Washington. ``We will not be intimidated. Our will and our resolve are firm. Democracy is taking root, and there's no turning back.''

The Fallujah attack, three months before the U.S. is scheduled to hand power over to Iraqis, pointed up the vulnerability of civilians working for relief groups and companies rebuilding utilities and other basic services to shore up the economy. Two guards for General Electric Co. engineers were shot dead Sunday in northern Iraq near a power plant project.

The four contractors killed today were Americans, State Department spokesman Adam Ereli said in Washington.

`Desperate' Opposition

U.S. Brigadier General Mark Kimmitt said in Baghdad that the Fallujah attacks were the work of a small group ``desperate to try to hold out and turn back the hands of time.'' He vowed that U.S. Marines would be sent in to root out those militants and impose order in the town, about 30 miles west of Baghdad.

Kimmitt said it was too early to evaluate the actions of Iraqi security forces in Fallujah and determine why there was no evident attempt to prevent the mutilation of the bodies.

The soldiers were hit by a bomb blast as they rode in a military vehicle in Anbar province, northwest of Habbaniyah, Kimmitt said.

In another incident, three British soldiers were injured southwest of the city of Basra, in the south, a spokeswoman for the Ministry of Defense said in a telephone interview in London.

Fallujah and Habbaniyah, about 10 miles west, are part of the so-called Sunni Triangle, a focus of anti-U.S. sentiment by Sunni Muslims loyal to ousted President Saddam Hussein.

Official Targeted

Two bodyguards for the governor of Diyala province and three bystanders were hurt in Baqubah in a car bombing today that killed the attacker, the U.S. said. The governor wasn't hurt, when the bomb went off next to his vehicle. Another Iraqi official, public works minister Nisreen Berwari, escaped an attack Sunday.

The deaths of the five Americans in the bombing brings to 291 the total number of U.S. military personnel killed in hostilities in Iraq since President George W. Bush declared the end of major combat operations on May 1.

Amid the violence, Iraqi officials said today the country's most important product, crude oil, is being pumped at a rate comparable to prewar flows.

Iraq is now pumping almost 2.5 million barrels of crude a day and hopes to raise that to 3 million by the end of the year, according to a statement from the country's delegation to an OPEC meeting in Vienna.

Exports are 1.9 million barrels a day. They should reach 2.2 million to 2.3 million barrels a day next quarter and stay at that level for the rest of the year, the statement said.

To contact the reporters on this story: Heather Langan in London at hlangan@bloomberg.net and Edward DeMarco in Washington edamarco@bloomberg.net.

Last Updated: March 31, 2004 16:13 EST