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Saudi security officials said the body of a man, possibly a Westerner, was found Sunday near the National Guard headquarters. But the city's police chief denied the body of a Westerner was discovered.

The police chief's denial, carried on the official Saudi press agency, did not make clear whether a body had been found but not that of a Westerner or whether no body was found at all.

Meanwhile, authorities were searching Sunday for an American apparently abducted by Al Qaeda (search)-linked militants who claimed responsibility for gunning down another American in the Saudi capital, the third killing of a Westerner in a week.

The kidnapping, the first of a Westerner in the kingdom, appeared to be a new tactic in a campaign of violence in the kingdom believed to be aimed at sabotaging the vital Saudi oil sector.

A statement purporting to be from Al Qaeda threatened to treat the abducted American as U.S. troops treated Iraqi prisoners — a reference to sexual and other abuses at Abu Ghraib prison (search) in Iraq.

Secretary of State Colin Powell said Saudi Arabia is mobilizing all of its resources against Al Qaeda-linked militants but, he added, "I think that there is more that they can do."

The Saudis can "build up their forces" and cut off funding for militants, he said on "Fox News Sunday." "There's probably more we can do with respect to intelligence exchange, and we are working at all of these," he said.

"The Saudis know that this is an enemy that is coming after them. The killing of foreigners ... is a direct attack against the Saudi regime. It's trying to disrupt normal commerce, disrupt the oil sector," Powell said on ABC's "This Week."

The Al Qaeda statement, posted late Saturday on an Islamic Web site, showed a passport-size photo of a brown-haired man and a Lockheed Martin (search) business card bearing the name Paul M. Johnson. The statement said he was born in 1955.

Word of the kidnapping came hours after an American, identified by the U.S. Embassy as Kenneth Scroggs, was gunned down in the Saudi capital. Scroggs was shot in the back as he parked in the garage at his home. The Al Qaeda statement also claimed responsibility for the shooting.

"We know that one American was killed and one American kidnapped," Powell said.

None of the gunmen have been caught in the fatal shooting June 6 of an Irish TV cameraman, Tuesday's slaying of an American contractor or Scrogg's slaying.

Saudi security officials, speaking on condition of anonymity, said authorities were searching for the assailants. Saudi forces, they said, stormed a suburban Riyadh house Sunday morning, arresting a man inside and confiscating a computer. It wasn't clear if he was linked to any of the past week's shootings.

Some 8.8 million foreigners work among 17 million Saudis in the kingdom, mostly in the oil sector, banking and other high-level businesses.

The British Embassy in Saudi Arabia announced Sunday it was authorizing the voluntary departure of nonessential staff and their families.

Spokesman Barrie Peach said the decision was not a response to Saturday events but rather was "the result of consideration over the last week."

British Airways also announced that its flight crews will no longer stay overnight in Saudi Arabia because of security problems.

The United States has urged all its citizens to leave the kingdom, and U.S. Ambassador James C. Oberwetter said Saturday that those who remain "should exercise the utmost caution."

The U.S. Embassy said it was working with Saudi officials to find the kidnapped American. A spokesperson said the embassy had no further details Sunday on the shooting or apparent abduction.

A car belonging to Johnson was found Saturday near Imam University, security officials said. Saudi press reports said the car was booby-trapped and later caught fire. The university is about 12 miles from the neighborhood where Scroggs was shot.

The purported Al Qaeda statement said Johnson is one of four experts in Saudi Arabia working on developing Apache attack helicopter systems and that the American killed worked in the same industry.

"Everybody knows that these helicopters are used by the Americans, their Zionist allies and the apostates to kill Muslims, terrorizing them and displacing them in Palestine, Afghanistan and Iraq," said the statement. It said Al Qaeda would release a videotape later with Johnson's confessions and its demands.

A Lockheed Martin spokesman confirmed Johnson was a Lockheed employee but declined to say what his job was. The spokesman also said Lockheed Martin was not aware of any employees who had been killed in Saudi Arabia.

A Saudi security source told The Associated Press that Scroggs worked for Advanced Electronics Co., a Saudi firm whose Web site lists Lockheed Martin among its customers. The office number on Johnson's business card was for Advanced Electronics.

"We have nothing to say," said an unidentified Advanced Electronics Co. employee who answered the phone Sunday.

Meanwhile, several Islamic Web sites were carrying links to a videotape — also purportedly from Al Qaeda — that claims to show Tuesday's killing of American Robert Jacobs.

The pan-Arab television station Al-Jazeera aired parts of the tape Sunday, showing two men surprising Jacobs as he tried to park in front of his garage then showing Jacobs writhing on the ground as an attacker fired from a hand gun.

Broadcast editor Yasser Thabet said the network followed its policy of avoiding overly graphic material in the tape.

Jacobs, 62, of Murphysboro, Ill., worked for U.S. defense contractor Vinnell Corp. (search)

The video, less than two minutes long, does not show any faces. It begins with men running in a garage and a voice yelling in English, "No, no, please!" A shot is fired, and the body of what appears to be a Western man falls to the ground. Two gunmen fire at least 10 more shots at the fallen man, then one kneels by his head and motions as if he is beheading him.

The statement and the videotape were attributed to Al Qaeda in the Arabian Peninsula. There was no way to verify their authenticity. The same group claimed responsibility for a shooting and hostage-taking spree in the eastern Saudi city of Khobar on May 29-30. That attack in the hub of the Saudi oil industry killed 22 people, mostly foreigners.

Militant attacks against Westerners, government targets and economic interests in the Saudi kingdom have surged in the past two months, despite a high-profile campaign against terrorists the government began after bombings last year.

Crown Prince Abdullah (search) urged Saudis to "inform me personally of anyone who has deviated from religion, attacked (it) or is an extremist. ... They (militants) will not slip away from the hand of justice."