By Sewell Chan and Karl Vick
Washington Post Foreign Service
Friday, April 2, 2004; Page A01

BAGHDAD, April 1 -- U.S. officials vowed Thursday to hunt down those responsible for the killing and mutilation of four American civilians in western Iraq and acknowledged that ordinary Iraqis, not just religious extremists, are behind some of the violence against the American-led occupation.

One day after the incident in Fallujah, in which insurgents killed four American security guards and enraged townspeople burned and hung their corpses, the effects of the ambush and its gory conclusion could be felt throughout the Iraqi capital.

The top U.S. military spokesman in Iraq vowed a forceful response by the Marines, who he said would reestablish control of Fallujah and pacify its restive population. The Marines set up traffic control points around the city, restricting vehicles from entering and leaving.

In a show of force, U.S. troops patrolled Baghdad in numbers not seen in weeks. Armored Humvees, M1-A1 Abrams tanks and Bradley Fighting Vehicles, as well as soft-skinned troop trucks, coursed through the city while AH-64 Apache attack helicopters flew overhead.

A four-day international exposition scheduled for next week and billed as Iraq's largest postwar business gathering was canceled after diplomats said it would be impossible to protect Americans attending the event, which would have coincided with the anniversary of Baghdad's fall. Organizers of Destination Baghdad Expo said the decision to postpone the event indefinitely was "jointly made" with occupation officials.

Also Thursday, the military announced that a roadside bomb in a marketplace in Ramadi, 30 miles west of Fallujah, killed six Iraqi civilians and wounded four others. The bomb was planted in a vehicle, but it was not clear whether the bomber was among the casualties, said Air Force Lt. Col. Steve Murray, a military spokesman.

Official responses to Wednesday's attack began with indignant condemnations but ended with unanswered questions.

The U.S. administrator for Iraq, L. Paul Bremer, called the killings an act of "cowards and ghouls" and vowed to seek justice.

"Yesterday's events in Fallujah are a dramatic example of the ongoing struggle between human dignity and barbarism," Bremer said in a speech to graduates at the Baghdad Police Academy. "The acts we have seen were despicable and inexcusable. They violate the tenets of all religions, Islam included, as well as the foundations of civilized society."

He said of the victims: "Their deaths will not go unpunished."

Bremer insisted that the attacks would affect neither the planned handover of political power to an interim Iraqi government on June 30 nor the plans to reconstruct Iraq. "These murders are a painful outrage for us in the coalition, but they will not derail the march to civility and democracy in Iraq," he said.

Army Brig. Gen. Mark Kimmitt, the military spokesman and deputy director of operations for the joint task force in Iraq, promised that the Marines would quell the violence in Fallujah.

"We are not going to do a pell-mell rush into the city," Kimmitt said. "It's going to be deliberate, it will be precise and it will be overwhelming."

For hours on Wednesday, much of Fallujah was lawless. Shops were closed and restaurants emptied as a mob dismembered the charred corpses of the victims and dragged their remains through the streets, using a donkey-drawn cart and two automobiles.

Iraqi law enforcement officials avoided the scene. Not until 8 p.m. did members of the Iraqi Civil Defense Corps, created under U.S. supervision, enter Fallujah to retrieve what was left of the corpses. Marines based just east of Fallujah kept out of the city nearly all of Wednesday and Thursday.

Kimmitt defended the decision to stay away following the attack. "While it was dreadful, while it was unacceptable, while it was bestial, a preemptive attack into the city could have taken a bad situation and made it even worse," he said.

He later added: "We will be back in Fallujah. It will be at a time and a place of our choosing. We will hunt down the criminals. We will kill them or we will capture them, and we will pacify Fallujah."

For at least two months, U.S. officials have blamed the continuing insurgency primarily on a loose network of religious extremists, terrorist cells and foreign troublemakers. But there was no such talk on Thursday. Instead, officials focused on the threats within -- from Iraqis who continue to battle the occupation nearly a year after the fall of former president Saddam Hussein.

"This is a cancer inside the society of Iraq that shows no indication of leaving anytime soon," Kimmitt said at a news conference. "Although small, it's a malignant cancer, and we need to take care of this together with the people of Iraq, the Iraqi security forces and the coalition forces."

Kimmitt said the military considers a wide variety of Iraqi groups as possibly involved in the attack, including Fallujah residents, former officials of the Iraqi intelligence services, "the inner circle of Saddam's privileged few" and members of Saddam's Fedayeen, a now-outlawed militia loyal to Hussein.

The military, Kimmitt added, is looking for people who took part in the desecration of the bodies, which was videotaped by the Associated Press and broadcast around the world. "We have a significant interest in finding them and talking to them," Kimmitt said.

By day's end, however, it was not clear what the victims -- who were employees of a security firm that has several U.S. government contracts -- were doing in Fallujah. Their company, Blackwater Security Consulting of Moyock, N.C., declined to identify the four employees. The company said they helped to protect food convoys in the area but would not offer any details about their work.

An overwhelming majority of Baghdad residents interviewed Thursday expressed revulsion at the spectacle in Fallujah, which was beamed by Arabic-language satellite channels into homes across the country.

Sana Mohammed Ali discussed the attacks in a dress shop with a friend. She quoted the son-in-law of the prophet Muhammad: "We all know Imam Ali's saying: 'A human being is either a brother to you in Islam or your equal in humanity.' The people who killed them are lunatics. We felt sorry when we saw the scene. We felt very bad about it."

Many Iraqis frowned and noted that the Koran specifically forbids mutilation of the dead.

"It was all very wrong," said Jasim Mohammed in the Adhamiya neighborhood, which is known for revering Hussein and resisting the occupation. "People don't approve the action yesterday. They say it was a big mistake."

But others said they understood the attack that preceded the mutilations. "I watched the TV and I disapproved," said Ahmed Mohammed, a mechanic in Adhamiya. "But the people who dragged the dead bodies probably either lost a loved one to the Americans or saw their father arrested and humiliated by soldiers who put their boots on his head."

Special correspondent Khalid Saffar contributed to this report.