The U.S. government yesterday warned all Americans traveling or living abroad to take extra security precautions from now through the first week in January because intelligence officials have obtained "credible information" that terrorists are planning attacks "specifically targeting American citizens."

The global caution, issued by the State Department less than three weeks before people around the world ring in the new millennium, said the intelligence information "indicates that attacks could be planned for locations . . . where large gatherings and celebrations will be taking place."

The advisory did not name specific terrorists who are suspected of making preparations to harm Americans. Administration officials were cautious in discussing terrorist organizations but indicated the group headed by fugitive Saudi businessman Osama bin Laden is the most important organization seeking to undermine U.S. interests.

State Department spokesman James B. Foley said the government had no evidence that Americans who remain in the United States will be in danger, but he said U.S. citizens are among the targets of attacks that could occur anywhere else in the world.

The State Department issues what it calls "worldwide cautions" relatively frequently--whenever it believes that citizens might be in harm's way. Often, such warnings follow specific U.S. military or economic actions that could provoke retaliation by anti-American groups, and sometimes they are restricted to particularly dangerous regions of the globe.

Yesterday's warning, issued in the late afternoon, was the fifth since early October.

But government officials said yesterday's caution signals a heightened degree of government concern. "This means we have specific and credible information that terrorists are planning something," said one senior administration official.

The threat to Americans that prompted yesterday's warning is comparable in magnitude to ones that intelligence officials detected this year during the war in Kosovo or the ones that arose from Iraq during the 1991 Gulf War, according to one official in the State Department's bureau of consular affairs.

"This sounds to me fairly larger than many of the ones we've put out," the official said, noting that it comes at a time when "people are already worried because of Y2K. You don't want to over-alarm them, but if we have this information, there's an obligation to tell them."

"There have been a slew of threat reports over the past few weeks, mainly bin Laden related," the Los Angeles Times quoted a government source as saying. "And then one emerged in the past couple of days that seemed much more credible and specific than all the others."

Bin Laden, who is living in Afghanistan under the protection of its ruling Taliban militia, has been indicted by a New York grand jury on charges of conspiracy and murder in the 1998 bombing of U.S. embassies in Kenya and Tanzania, which killed more than 220 people.

Earlier this year, the Clinton administration banned U.S. trade with and investment in Afghanistan because the Taliban refused to deliver bin Laden for prosecution. In mid-October, the U.N. Security Council gave the regime a month to produce him and said it would face similar sanctions imposed by the United Nations unless it complied.

In late October, a Taliban representative traveled to Washington to discuss the case with the State Department's assistant secretary of South Asian affairs. But the regime ultimately did not expel bin Laden, and last month the United Nations banned international flights to Afghanistan and froze its overseas assets.

The State Department issued its last global caution when the U.N. sanctions took effect.

The new warning says that attacks could occur any time from now through New Year's and the first week in January, when the month-long Muslim holy days of Ramadan end. The warning urges Americans abroad to "avoid large crowds and gatherings, keep a low profile, and vary routes and times of all required travel."

The caution also urges U.S. citizens abroad to stay in touch with U.S. embassies and consulates for further information.

Although federal officials said they have no evidence that Americans are at risk domestically, the advisory did not make entirely clear that the threat exists only on foreign soil.

D.C. Police Chief Charles Ramsey said yesterday that, with large celebrations planned for the Mall throughout the New Year's weekend, "it is no surprise to anyone that Washington could potentially be viewed as a target." However, Ramsey said, "Quite frankly, I think our biggest problem is going to be traffic control and crowd control because we're looking for a lot of people to come out."

Staff writer Sari Horwitz contributed to this report.