In this hilly town along the Euphrates River, people recall how Mohammed Nayil Jurayfi used to boast that his black Toyota Avalon had belonged to a senior Baath Party official -- until Jurayfi confiscated it on orders from U.S. Army officers.

His seizure of the Toyota and five other cars had been controversial, leading one local man to call him "an American collaborator" and another "a partner with the enemy."

But Jurayfi, an influential tribal leader who proclaimed himself mayor of Haditha after Saddam Hussein's government dissolved, was unruffled, according to relatives and colleagues. He was so proud of his relationship with the U.S. military that he kept a framed citation of thanks from an American officer on his mantel.

On Wednesday afternoon, as he was returning home from his office with his youngest son, Ahmed, at least two gunmen sprayed his Toyota with dozens of bullets as it rounded a corner, police officials said. Jurayfi and Ahmed were killed instantly, the officials said.

In Haditha today, there was no doubt about why the mayor was killed.

"He was too close to the Americans," said Abdullah Jurayfi, the mayor's cousin, as he sat at a wake in a long tent. "That was his big mistake."

In recent days, insurgents seeking to end the U.S.-led occupation of Iraq have broadened their targets from military personnel to Iraqis deemed to be collaborating with soldiers and civilian reconstruction specialists. Many Iraqis are too scared to work with Americans, which creates another troubling obstacle for the U.S. program to rebuild this country.

Last week, police officers in Fallujah, about 35 miles west of Baghdad, complained that they were being targeted by resistance fighters because U.S. military police were in the town's police station. This month, seven new Iraqi policemen trained by the U.S. military were killed when a bomb exploded during their graduation ceremonies in Ramadi, about 60 miles west of Baghdad. Last month, the director of electricity distribution for the western half of Baghdad, who had worked closely with U.S. officials, was killed in her home.

On Monday night, a car bomb detonated prematurely outside a police station in Baghdad, decapitating one of the assailants in an attack that one Iraqi officer said was intended "to frighten people away from the Americans."

"Working with the Americans has become very dangerous," said police Lt. Ahmed Hassan Mohammed in Haditha, 125 miles northwest of Baghdad. "We have become targets, too."

A group calling itself the Iraq Liberation Movement distributed leaflets here today that said that "the heroes of the Iraqi resistance have begun to target some Iraqis and Iraqi police stations in order to liquidate some of the symbols of treason and espionage." The previously unheard-of organization warned residents "not to come close to vehicles and buildings used by the occupying power . . . so that the heroes of our movement can organize their operations."

Police officials said they did not know whether the group was responsible for Jurayfi's death. Capt. Khudeir Mohammed Sael said several municipal employees received leaflets on Wednesday warning them not to go to work. The documents were signed by an organization that called itself Liberating Iraq's Army, which this week claimed responsibility for several recent attacks on U.S. forces.

"We don't know who is behind this," Sael said. "But we are sure it is people who do not want us to be friendly with the Americans."

Sael and others said Jurayfi's death was just the latest in a series of attacks on people in Haditha deemed to be collaborating with U.S. forces. On Tuesday morning, he said, the house of a police lieutenant colonel was firebombed, killing two of his teenage children. Five hours before, the officer had served tea to several American soldiers in his garden, Sael said.

Last week, a rocket-propelled grenade was fired at the home of a prominent tribal sheik who had met with U.S. troops the day before, people said.

"There is a pattern here," Sael said. "It is a very frightening pattern."

U.S. officials in Baghdad said they were concerned about the increasing frequency of attacks on Iraqis who have been working with Americans, although they cast the incidents as acts of desperation by insurgents who were too cowardly to challenge uniformed troops.

"It's a big problem when it comes to gaining the trust of our Iraqi partners," one senior official said. "We need the police officers and the teachers and the electricity workers and the other government workers to feel safe enough to work with us."

In Haditha, several police officers said continuing to work with Americans would be too risky.

Mohammed, the police lieutenant, said officers in Haditha did not conduct joint patrols with the U.S. military as police in other Iraqi cities do. Nor do they wear new, American-supplied blue shirts. Instead, he said, cooperation was far more discreet.

"We don't drive through the city with them," Mohammed said, who wore the same khaki uniform officers in the town wore before the war. "That would be foolish."

Outside the station, away from fellow officers, Mohammed insisted in a soft voice that the town's police force needed help from the Americans, but he said he feared the consequences of receiving more assistance. "We want to work with the Americans because we need new equipment. We need new radios and cars. We need training," he said as he stood next to Jurayfi's bullet-riddled car, which had been towed to the station. "But we also know that if people see us working together, they will shoot at us like they do to the Americans."

The same sense of fear pervades the market in this overwhelmingly Sunni Muslim town that has prospered as a trading outpost on the road to Syria. Merchants almost uniformly stated they would not sell even a single can of soda to an American soldier -- but not always for the same reason.

"We're not going to have anything to do with the occupiers," growled Sahib Hekmat, the portly owner of a small dry-goods shop. "Now, if we discover anybody in the town who is cooperating with the Americans, we won't visit their home. We won't even say hello to them in the street."

A few doors down, another shopkeeper also insisted he would not sell anything to passing U.S. soldiers, though he said he did not object to their presence in Iraq. "It will cause me trouble," the shopkeeper said.

Whether Jurayfi was apprehensive about his relationship with U.S. forces was a matter of debate today. Sael said the mayor asked the Americans to provide him a security detail, or at least a permit to carry a machine gun, but both requests were turned down. Sael also said a U.S. patrol drove by Jurayfi's car shortly after the shooting but did not stop to help.

"If you deal with the Americans, they come to you and promise you so much, but when something bad happens, they leave you like they do not know you," he said.

But Abdullah Jurayfi maintained that his cousin was not worried about security and regarded guards as an embarrassment. "He thought it was shameful to have protection in his own city," he said.

No matter how he felt about his safety, the mayor apparently made little effort to play down his ties to the U.S. military, which, by several accounts, were not extensive.

A former Baathist who broke with the former ruling party in the 1970s and was imprisoned repeatedly for alleged pro-Syrian leanings, Jurayfi staked claim to the mayor's office as soon as Hussein's government fell.

He dispatched police to the streets and called on local tribal chiefs to help maintain order. His actions are regarded by many as the reason Haditha escaped the looting that befell other parts of Iraq.

When troops from the 3rd Armored Cavalry Regiment moved into the area, he became a trusted intermediary for U.S. commanders. When they needed intelligence on former Baathists, his relatives said, he dished. When they needed help confiscating government automobiles from the town's former leaders, he volunteered to do the job.

In an interview with a Post correspondent in late June, Jurayfi pronounced himself "very proud" of his citation from the U.S. Army.

He noted wryly that he had escaped three death sentences, which were commuted because of his prominence as a tribal leader. A jovial character and the father of 11 children, Jurayfi said he wanted to enter national politics in the new Iraq.

"I'm very optimistic about the future," he said in the sitting room of his large walled home. "God willing, these problems we have will disappear soon."

At the police station, officers saw an omen in the charred remains of his Toyota, which caught fire after a bullet pierced the gasoline tank. The only item not fully burned in the car was a piece of Iraqi currency. Although singed around the edges, the smiling visage of Hussein was clearly evident.

"He's still haunting us," Sael said as he looked at the bank note.

As he walked away, he said he would not repeat the mayor's "mistakes" of dealing with Americans.

"We must change what we do," he said. "If we don't, they will kill us one by one."

Correspondent Peter Finn contributed to this report.

Iraqi police gather by the bullet-riddled car of Haditha's former mayor, Mohammed Nayil Jurayfi, who often gave information to U.S. troops. Mohammed Nayil Jurayfi, who was known to be pro-U.S., and his son Ahmed were killed Wednesday. An Iraqi shop owner speaks to a U.S. soldier while another soldier stands guard. Many shopkeepers, fearing retribution, have stopped serving troops.