Citing what he said was unusually specific information warning of al Qaeda terrorist attacks on individual financial buildings in Washington, New York City and northern New Jersey, Homeland Security Secretary Tom Ridge today raised the threat level for the financial services sectors in the three locations.

Ridge said that the information pointed to five possible, specific targets: the International Monetary Fund and World Bank headquarters in Washington; the New York Stock Exchange and the Citicorp building in New York; and the Prudential Bache building in Newark, N.J. Ridge said the information indicated the attack would probably be by a car or truck bomb.

The authorities raised the threat level for the financial areas in the three places to orange, or "high," on the government's color-coded scale. The rest of the nation remains at yellow, or "elevated."

Ridge made the announcement in a televised news conference at 2 p.m. after briefing local officials and news media executives in a conference call an hour earlier. His presentation, which he described as "sobering," was a departure from previous warnings, which have tended to be relatively vague and non-specific.

He said it was the first time the government has chosen to issue a warning in "such a targeted way." There is "a level of detail that is very specific, . . . multiple reporting streams in multiple locations. It is alarming in both the amount and specificity," he said.

Ridge said intelligence, law enforcement and homeland security officials had amassed "extraordinary detail" about the possible attacks in the last 24 to 36 hours.

"This is not the usual chatter," Ridge said during his conference call. "We have in this case a most unusual set of circumstances, a convergence of information that compels us to talk publicly about specific potential targets."

Ridge said security authorities in the specific locations were already taking new anti-terrorism measures and that people will notice them. They include erecting broader buffer areas between the streets and the buildings, and more rigorous checks of individuals and packages moving into the specific areas.

He suggested that everyone in those areas should be especially vigilant for suspicious or unusual activity but, in consultation with their own security officials, should probably go about their business.

"As sobering and difficult as this is," he said, he hoped "folks who work at those particular sites would have the resolve to say 'we know what you know and we're going to go about leading our lives and not let threats turn us into fortress America.' "

Administration officials, who typically stress that threat information is vague and base their alerts largely on the volume of monitored communications, said the intelligence was some of the most specific they had ever received. A senior administration official, who spoke on condition of anonymity because of the sensitivity of the topic, called the information "much more specific than we've ever been able to provide before."

Calling it the highest level detail he has seen concerning a possible terrorist strike in the past quarter of a century, the official described how attackers have identified the average daily flow of pedestrians outside the targeted buildings and security procedures inside.

In the course of their communications, the officials said, the terrorists note possible sewer system escape routes, the locations of nearby fire departments and police precincts, and whether individual security guards carry guns.

"Getting up to the higher floors is not very difficult if you go there midweek, as I did," one suspected terrorist was quoted as saying. In a separate communication, a potential attacker warned, "You must provide an adequate cover story."

Ridge credited, among other sources, U.S. "offensive" military operations for obtaining the information. "The sources come to us as benefit of the work [of] a lot of folks -- including our military, CIA and our global allies."

"There may be more to come," Ridge said. "We decided not to wait until we were done," he said. The government felt that "we better get out with what we know now."

Ridge said he notified mayors and governors in the area before the conference call. He said that the hour before he went on television, officials were still "in the process of trying to put security into place." "We've got some teams right now sitting down with some of the security professionals at these venues, sharing with them in detail what we know," he said.

Considering the nature of the targets -- all financial institutions -- Ridge was asked at the news conference whether he believed al Qaeda was trying to bring down the U.S. economy.

"These are significant institutions that relate to our leadership role in the international economy," he said. But attacks on them would not "undermine the greatest economy in the world. . . . So to a certain extent it's almost iconic."

"This is a hallmark of al Qaeda's planning. They are meticulous," he said. "There has been extensive reconnaissance . . . over an extensive period of time."

Ridge said he did not believe the alert would disrupt the Republican National Convention, which is to begin Aug. 30 in Manhattan. "New York operates at a level of security that is as good as any in the country," he said. "It's a very well-protected city."

The administration first released the information during the 1 p.m. conference call, with the agreement the information would be withheld until Ridge spoke on television. The administration said that was because officials knew the announcement would create anxiety and raise lots of questions with the public.

Ridge said authorities would install "additional protective measures" around the targeted buildings, and would hope to disrupt the terrorists' plans by revealing them to the public.

Dealing with car and truck bombs is "one of the most difficult tasks we have in the war against terror," he said.

The International Monetary Fund and the World Bank Group buildings together occupy several square blocks in the Foggy Bottom area of Northwest Washington.

Their sites are familiar settings for large and occasionally unruly demonstrations by people critical of the powerful role that the two institutions play in the global economy.

The World Bank, at 18th and H Streets, is primarily a development bank, which provides loans and assistance to low income countries around the world. It is divided into associated institutions, among them the International Bank for Reconstruction and Development, the International Development Association, and the International Finance Corporation

The IMF, at 700 19th St., NW, was set up to ensure the stability of the international monetary and financial system. It provides advice and sometimes financial assistance to nations facing potential or actual economic crises, a role that has made it controversial in some quarters.

While the World Bank and IMF are international institutions, with international directors and international funding, the United States exercises a dominant role because it is the world's largest economy and is the largest donor to them.