Jordanian security forces have arrested a group of Afghan-trained Arabs who U.S. officials said were planning to attack American and other targets in Jordan, Prime Minister Abdul-Raouf Rawabdeh announced today.

Rawabdeh said the kingdom's security forces had seized 11 Jordanians, an Iraqi and an Algerian returning from Afghanistan who planned "to carry out operations in the Jordanian arena."

The announcement followed a U.S. statement Tuesday that followers of Osama bin Laden had been arrested in the Middle East and had been planning attacks against Americans at year's end. Bin Laden is the Saudi-born millionaire based in Afghanistan whom the United States has accused of masterminding the bombings of the U.S. embassies in Kenya and Tanzania last year.

In Washington, White House spokesman Joe Lockhart said: "We certainly believe these were members of bin Laden's organization that posed a threat to Americans. We are following closely a number of threats and continue to be very vigilant on that front."

The State Department has issued several warnings lately to Americans living or traveling abroad about the danger of attacks, and there is some concern that overseas millennium celebrations could provide a target for terrorists.

The CIA, which has a special task force devoted to targeting bin Laden's global terrorist network, played a central role in gathering the information that led to the arrests in Jordan, U.S. officials said this week. However, a CIA spokesman today denied the agency had been involved.

Rawabdeh made no reference to bin Laden or the nature of the targets in Jordan but said those arrested had received military training in camps in Afghanistan and entered Jordan on forged passports. Three other members of the ring remain at large outside Jordan, he said.

[In Washington, a State Department spokesman said the government is in contact with Pakistan about a reported arrest near its border with Afghanistan, according to the Reuters news service.

[The spokesman, James Foley, was responding to questions during a telephone briefing about whether more arrests had been made in relation to the public warning his department issued, apart from the 13 people detained in Jordan.]

Several dozen suspects linked to bin Laden have been arrested around the world since the CIA began focusing on him in earnest in 1996, and the agency says it has amassed a wealth of information about his loose network of followers, proteges and beneficiaries.

Jordanian security forces, which are generally regarded as efficient, have focused on Jordanians with connections in Afghanistan for a number of years, but Amman provided no further details on the identity, movements or activities of the suspects or about what kind of American targets might be at risk. Rawabdeh did not say when the arrests took place, but a Jordanian source said they were made earlier this month.

Bin Laden and some groups and individuals associated with him are based in Afghanistan, whose Islamic Taliban government has provided him with a haven. Bin Laden has built his network largely among the Islamic veterans of the Afghan war against the Soviet Union in the 1980s, and the Taliban has refused to hand him over to the United States or a third country for trial on terrorism charges.

Islamic volunteers from several Arab countries, including Jordan, fought in the Afghan war and maintain ties with Muslim militants there. "Afghanistan is still serving as a base for training terrorists from all over the world," said Yoram Schweitzer, an Israeli expert on terrorism at the International Policy Institute for Counter-Terrorism near Tel Aviv. "You can find Afghan alumni in the cells that have been operating in Jordan."

Schweitzer added: "It doesn't have to be that bin Laden himself is responsible. It could be the people connected to bin Laden. . . . He has disciples or people financed by him, and those people may have recruited people from Middle Eastern countries to be trained there."

U.S. officials said on Tuesday that Washington had told the Taliban government it would hold it responsible for any attacks on Americans by followers of bin Laden. The State Department said the United States had delivered the warning Monday following the arrests in Jordan.

On Saturday, the United States issued a worldwide warning to citizens traveling abroad before the New Year and through the Muslim fasting month of Ramadan, citing "credible information that terrorists are planning attacks."