Bloodied bodies shown by Saudi news services Saturday were four leaders of the group that asserted responsibility for the beheading of an abducted American contractor in the capital of Riyadh, according to government officials there and in Washington.

Authorities in Saudi Arabia were continuing to search Riyadh's outskirts for the body of the kidnapped American, Paul M. Johnson Jr., an employee of Bethesda-based Lockheed Martin Corp., a senior Saudi official told reporters in Washington.

That statement by Adel Jubeir, a foreign policy adviser to Crown Prince Abdullah, contradicted earlier reports that said Saudi officials had already recovered Johnson's decapitated corpse, pictures of which were posted on the Internet Friday by a group calling itself al Qaeda in the Arabian Peninsula.

Saudi security forces said the al Qaeda group's leader, Abdulaziz Muqrin, and three others whom authorities had blamed for recent attacks on Westerners were among those killed in a gun battle Friday.

Images broadcast Saturday on state-run television and an all-news Saudi Arabian satellite channel showed what officials said was Muqrin's body. Saudi officials identified the other members of the al Qaeda group who were killed as Faisal bin Abdulrahman Dakheel, Turki bin Fehaid Mutairi and Ibrahim bin Abdullah Duraihem.

In Washington, Jubier said the deaths and the arrest of 12 other members of the group were "a blow to al Qaeda in Saudi Arabia" that had "substantially weakened their organization."

"We will continue to pursue them with vigor until we eliminate them from our midst," Jubeir said. "We are resolved to fight terrorism, those who fund it and those who justify it. We will show no mercy."

Jubier said one Saudi security officer was killed and two were injured in Friday's shootout. Security forces also said they seized guns, rocket-propelled grenades, hand grenades, 16 pipe bombs and three cars, including one that may have been used in a June 6 attack on a BBC television crew that killed an Irish cameraman.

A message on an Islamist Web site Saturday said the government's claims that it had killed Muqrin were "aimed at dissuading the holy warriors and crushing their spirits," the Associated Press reported.

Johnson's kidnapping and the manner of his killing marked a new kind of assault on the American presence in the oil-producing kingdom. Radicals say that vengeance for the occupation of Iraq is part of the reason for the campaign, which has led many Americans to leave the country and made those who remain fearful of streets they once found safe. The ultimate goals, the groups say, are to drive foreigners out of the kingdom and overthrow the House of Saud royal family.

On Friday, President Bush denounced Johnson's killers as "barbaric people" trying to intimidate Americans. "The murder of Paul shows the evil nature of the enemy we face," Bush said in Fort Lewis, Wash. "They're trying to shake our will. They're trying to get us to retreat from the world. . . . America will not be intimidated by these kinds of extremist thugs."

Johnson was reported missing by his family on June 12, the same day that another American contractor who worked out of Johnson's office, Kenneth Scroggs, was killed by gunmen as he drove into his garage in Riyadh.

Last weekend, the group announced it was holding Johnson and said he would be treated as Muslim detainees were treated in Iraq's Abu Ghraib prison, scene of abuse by U.S. jailers, and Guantanamo Bay.

On Tuesday, Muqrin's group released a short video showing a blindfolded Johnson. A masked man, identified in a caption as Muqrin, threatened to execute him within 72 hours unless Saudi officials released an unspecified number of fellow jihadists from prison. The Saudi government refused and launched an effort to find and rescue Johnson.

According to Saudi spokesmen, the operation drew on 15,000 security personnel, including fire departments familiar with streets and neighborhoods. More than 1,200 homes had been searched by Thursday night.

In addition, the U.S. government dispatched 20 FBI agents to Saudi Arabia to assist in the search. The presence of American agents on Saudi soil was a sensitive subject for Saudi government officials, who played down the U.S. role and bristled at the suggestion that they were unable to control the insurgency.

Prince Nayef, the Saudi interior minister, said in an interview with the French newspaper Le Figaro that the Saudi government did not need outside assistance. He noted that the United States has had difficulty finding terrorist suspects elsewhere, singling out Abu Musab Zarqawi, a radical who has eluded capture in Iraq despite a $25 million reward offer. Zarqawi has claimed responsibility for beheading another American, Nicholas Berg, in a kidnapping in Iraq this year.

In the days leading up to the deadline, Johnson's relatives and friends made emotional appeals on television for his release, telling the kidnappers that he was a friend of Muslims and deeply interested in their culture.

"Please release my father," Johnson's son, Paul Johnson III, told al-Arabiya television a few hours before the station reported the execution. "He is an innocent man. He loves Muslims. Saudi Arabia was his home." Johnson's wife, Thanom, made a similar plea in television interviews.

On Friday, the kidnappers posted a statement on an Islamic Web site announcing his death and included three photos of his remains.

Johnson worked on Apache attack helicopter systems for the Saudi government. His kidnappers said he was singled out for that reason. "Let him taste something of what Muslims have long tasted from Apache helicopter fire and missiles," they said in a statement posted on the site. "The infidel got his fair treatment."

"To the Americans and whoever is their ally in the infidel and criminal world and their allies in the war against Islam, this action is punishment to them and a lesson for them to know that whoever steps foot in our country, this decisive action will be his fate," the statement said.

James C. Oberwetter, the U.S. ambassador to Saudi Arabia, confirmed Johnson's death. "The inhumanity of the crime exceeds all boundaries of civilized peoples," he said in a statement.

On Thursday, the U.S. Embassy in Riyadh issued a fresh warning to Americans in Saudi Arabia, saying that there was "credible information indicating that extremists are planning further attacks against U.S. and Western interests." The warning added that Americans living in private residences -- as opposed to the guarded compounds that house many expatriates -- were being "specifically targeted."

On April 15, the State Department urged all Americans to leave the kingdom and has ordered the evacuation of all non-essential embassy personnel. For the past two months, all Americans remaining in Saudi Arabia have been asked to register their presence with the embassy.

In a radio interview Friday, Secretary of State Colin Powell said he hoped new security measures "will encourage people to stay" in Saudia Arabia. "If they leave, then the terrorists have won," Powell said on "The Michael Reagan Show." "And I don't think either the Saudis, the Americans, or these brave folks who work in Saudi Arabia want the terrorists to win."

American workers, most of them with the oil industry, and dependents used to number close to 35,000. Embassy officials said on Friday they did not know how many had left.

Lockheed began evacuating employees' family members from the country in April after the State Department issued its warning. Lockheed, the Pentagon's largest contractor, declined to say how many of its workers remained in Saudi Arabia or to discuss what security precautions it was taking.

"Paul bravely carried out his duties, and the news of his sudden loss is a shock to everyone in the Lockheed Martin family," the firm's two top executives, Chairman and CEO Vance Coffman and President Robert J. Stevens, said in a memo to employees. "We grieve along with his family."

Lockheed employees have sent 700 e-mails and letters to Johnson's family during the last week expressing remorse and condolences, according to company spokesman Tom Jurkowsky. "It's a different mood around here. It's numbing," Jurkowsky said.

Saudi Arabia is the birthplace of al Qaeda founder Osama bin Laden and the leading financial backer of conservative Islamic causes around the world. From the late 1970s until 2001, an estimated 15,000 Saudis trained at camps in Afghanistan and helped fuel religious warfare across the Middle East and northern Africa.

While many militant leaders, including bin Laden, have labeled the Saudi royal family corrupt for years and called for its ouster, until last year the kingdom was largely spared attacks from within. Violence picked up last May, when local groups allied with al Qaeda mounted a car bomb attack on a Western residential compound in Riyadh, killing 35 and sparking a limited but open revolt against the government.

Saudi security officials said they have arrested more than 300 militants since then and broken up the biggest terror cells, but have not been able to contain the violence. The attacks helped drive oil prices to historic highs and raised speculation that the House of Saud's hold on power might be slipping.

Muqrin's group is believed to have been behind a hostage-taking attack on a Western residential compound in Khobar last month that left 22 dead, as well as a suicide bombing in Riyadh last November that killed 17 and wounded more than 120.

Since then, the radicals have changed their tactics and have opted to target individual, unprotected Westerners rather than attempting to inflict mass casualties.

Mustafa Alani, a Middle East security analyst at the Royal United Services Institute in London, said the group wanted to avoid harming Muslims for fear of creating a backlash in the region. He also said that more kidnappings were likely.

"This sort of operation is easy to execute," he said in a telephone interview. "It's also cheap and very effective. How hard is it to shoot or grab somebody on the street? Look at all this television coverage they've gotten in the U.S. They've now discovered this cheap and easy way to get publicity."

Stencel reported from Washington. Staff writer Renae Merle in Washington contributed to this report.