Updated

The Al Qaeda (search) group responsible for abducting and killing an American engineer says it was aided by sympathizers in the Saudi security forces, a claim that was denied by Saudi authorities.

Al Qaeda in the Arabian Peninsula made the claim in an account of the operation posted on an Islamic extremist Web site Sunday.

It said Saudi security forces provided uniforms and police cars to militants who then set up a fake checkpoint to kidnap Paul M. Johnson Jr. (search). The militants say they posed as police to stop Johnson's car, anesthetized him and carried him to another car.

"A number of the cooperators who are sincere to their religion in the security apparatus donated those clothes and the police cars. We ask God to reward them and that they use their energy to serve Islam and the mujahedeen," the article said.

In a separate article on the Web site, the group's leader, Abdulaziz al-Muqran (search), said Johnson was targeted because of his work on Apache attack helicopters for Lockheed Martin. Al-Moqrin and three other militants were killed Friday in a shootout with Saudi security forces after they beheaded Johnson.

Johnson "works for military aviation and he belongs to the American army, which kills, tortures and harms Muslims everywhere, which supports enemies (of Islam) in Palestine, Philippines, Kashmir," al-Moqrin wrote.

On Sunday, police continued their search for Johnson's body and other militants involved in his death.

Police cars, armored vehicles and a large contingent of emergency forces blockaded the al-Malaz area of Riyadh Sunday in a search for suspects, security officials said. Witnesses saw suspects fleeing into a house in the neighborhood after police fired at them at a traffic light.

Hours later, the blockade was lifted and security forces left. It was unclear whether anyone was arrested.

On Sunday night, scores of Saudi men, mostly in their 20s and 30s, paid visits to the bullet-pocked gas station where al-Moqrin and the three others were killed.

"This should be turned into a national monument," said Mohamed Ibrahim Shakir. "Every Saudi should come here and pray to God. We got rid of these terrorists."

Ibrahim al-Shamari, who was tending the station, said the militant leader was shooting at security forces from behind a refrigerator when he was killed.

One security officer was killed and two were wounded in the shootout, the official Saudi news agency reported.

Al-Moqrin is believed to have had a leading role in the recent rise of militant violence in the kingdom. Dozens of people have been killed in a string of bombings and attacks targeting foreigners.

Saudi King Fahd said Sunday that militants would not succeed in their aim to harm the kingdom.

"We will not allow this destructive bunch, led by deviant thought, to harm the security of this nation or affect its stability," he said in a speech to the advisory Shura Council.

Johnson was seized June 12, the same day Islamic militants shot and killed Kenneth Scroggs of Laconia, N.N., in his garage in Riyadh. Earlier that week, militants in the capital also shot and killed Irish cameraman Simon Cumbers, who was filming for the British Broadcasting Corp., and another American, Robert Jacobs, of Murphysboro, Ill.

Johnson's captors said they would kill him on Friday unless Saudi Arabia released jailed Al Qaeda militants.

Sunday's Al Qaeda article said the militants decided to behead Johnson when Adel al-Jubeir, foreign affairs adviser to Crown Prince Abdullah in Washington, declared that Saudi Arabia would not negotiate with the kidnappers.

The group said it beheaded Johnson, 49, of Eagleswood Township, N.J., when its deadline expired Friday.

Asked about the Al Qaeda statement in a televised interview, al-Jubeir said, "We have never negotiated with terrorists. We don't intend to do so.

"I believe what the Al Qaeda people were trying to do is trying to justify a murder that is unjustifiable under any faith or under any principle of humanity."