Radicals Kill American in Saudi Arabia

Hours later, Saudi security forces reported that they had tracked down and killed at least three militants, including the reputed leader of a group responsible for beheading 49-year-old Paul M. Johnson Jr., a native of New Jersey.

A group calling itself Al Qaeda in the Arabian Peninsula threatened Tuesday to kill Johnson within 72 hours unless the Saudi government freed imprisoned Islamist militants. Saudi officials refused, insisting that they wouldn't negotiate with terrorists.

In a statement posted with the grisly photographs on an Islamist website, the group said, "As we promised the mujahedin [holy warriors], we have beheaded the American hostage Paul Marshall after the deadline that the mujahedin gave to the tyrannical Saudi government passed."

Three pictures showed the decapitated remains of a man resembling Johnson. In one picture, a hand cradled the severed head. In another snapshot, the slain man was sprawled on his stomach, and somebody had balanced the head, face to the camera, atop his back.

In the United States, Johnson's death drew expressions of sorrow and condemnation from top U.S. government and business officials. President Bush said Johnson's death was part of efforts by "extremist thugs" to intimidate Americans.

"The murder of Paul shows the evil nature of the enemy we face," said Bush, who spoke to reporters after a speech to troops in Ft. Lewis, Wash. "These are barbaric people. There's no justification whatsoever for his murder, and yet they killed him in cold blood. And it should remind us that we must pursue these people, and bring them to justice before they hurt other Americans."

The State Department issued a heightened alert Friday evening, warning U.S. citizens throughout the Middle East and North Africa that further attacks were likely.

A State Department official, citing recent intelligence, said the U.S. Embassy in Riyadh, the Saudi capital, was urging all Americans to leave the kingdom.

"It's terrifying when you read all the threat reporting that's out there," the official said. "It's just unreal."

Johnson was kidnapped last weekend, on the same day militants gunned down another American worker in his garage in Riyadh.