Updated

Jordanian officials rounded up dozens of known Islamic extremists for questioning Tuesday in the assassination of American diplomat Laurence Foley as suspicion for the attack fell on Al Qaeda or the terrorist movement's sympathizers.

A Jordanian official, speaking on condition of anonymity, said most of those detained were Jordanians of Palestinian origin who belonged to militant Islamic cells. Some were released but others were held for further questioning; none had been charged.

One militant, sought in an attack on a police station last year, was apprehended Tuesday after a shootout with police near the southern town of Maan. He later escaped from a hospital but was not a suspect in Foley's assassination, officials said.

Foley, 60, an administrator at the U.S. Agency for International Development, was shot by a lone gunman at close range as he walked to his car in front of his home in Amman. The gunman escaped.

King Abdullah II and his wife, Queen Rania, visited the U.S. Embassy on Tuesday to sign a condolence book and meet briefly with Foley's widow, Virginia. In a televised interview, the king described the killers as "evil extremists" bent on harming Jordan and promised to bring them to justice.

Foley's slaying — the first such targeted shooting of an American diplomat in decades — stunned Amman's diplomatic and expatriate community, which had generally felt safe despite rising tensions in the Middle East.

The U.S. Embassy advised Americans to "exercise caution" and vary their travel routes. Jordanian officials said additional guards and plainclothes police would be provided to Western diplomats.

Police and paramilitary units planned roadblocks on major thoroughfares, especially at night, a Jordanian security official said.

Neither U.S. nor Jordanian officials would publicly link the killing to Al Qaeda, despite indications the terror network was planning attacks here long before Sept. 11 and the U.S.-led war against terrorism.

"We continue to have excellent cooperation from the Jordanians but at this time we do not have any information about who is responsible," White House spokesman Ari Fleischer said. "Of course we'd never rule that [terrorism] out ... but we do not have anything that I can indicate yet."

In Beirut, Lebanon, the prominent Arabic language newspaper An-Nahar speculated that the killing was the work of Al Qaeda sleeper cells that have threatened strikes against American targets. There was no way to immediately confirm independently the paper's report.

Jordanian authorities discounted a claim of responsibility by Shurafaa' al-Urdun, or the Honorables of Jordan. In a statement to an Arabic newspaper in London, the group said it killed Foley to protest U.S. support for Israel and the "bloodshed in Iraq and Afghanistan."

The group claimed responsibility for the killing last year of Israeli businessman Yitzhak Snir, who was slain near Foley's home. However, Jordanian police believe Snir was killed by common criminals and that Shurafaa' al-Urdun does not exist.

Nevertheless, the fact that Jordanian authorities were questioning Islamic extremists suggested that they were the focus of the investigation. Jordan has consistently denied any Al Qaeda cell exists in the kingdom.

"Jordanian intelligence has been exceptionally good at monitoring and disrupting various [Al Qaeda] efforts," said Magnus Ranstorp, a Mideast terrorism expert at the University of St. Andrews in Scotland.

However, Ranstorp said Al Qaeda and its allies have not given up trying to destabilize Jordan and establish "an Islamist regime on Israel's doorstep."

Weeks ago, the U.S. Embassy warned Americans in Jordan to be vigilant after receiving unconfirmed reports that Al Qaeda was planning kidnappings of American diplomats. A number of Jordanians of Palestinian descent who are living abroad also are said to have close ties to Al Qaeda.

Even if no direct link to Al Qaeda is found, Ranstorp and other analysts believed the killers were probably inspired by Al Qaeda at a time when anti-Americanism is on the rise because of U.S. threats of war against neighboring Iraq and the crisis between Israelis and Palestinians.

"Al Qaeda is not an organization anymore, it is a concept," said Jordanian political analyst Labib Kamhawi. "There is a lot of appeal for the concept itself."

Ranstorp noted that evidence uncovered in Afghanistan showed that Al Qaeda had trained operatives in assassination techniques.

"On balance, I would be surprised if there wasn't any foreign participation," he said. "Al Qaeda does not have membership cards, and as such, linkages can occur on many different levels."