The federal government raised the terror alert level yesterday to orange for the financial services sectors in New York City, Washington and Newark, citing the discovery of remarkably detailed intelligence showing that al Qaeda operatives have been plotting for years to blow up specific buildings with car or truck bombs.

Homeland Security Secretary Tom Ridge said the newly acquired information points to five potential targets: the International Monetary Fund and World Bank headquarters in Washington; the New York Stock Exchange and Citigroup Center in New York; and the Prudential Financial building in Newark.

The intelligence shows that al Qaeda has been methodically casing those buildings, and perhaps others, since well before the Sept. 11, 2001, attacks on the Pentagon and World Trade Center, and also since then, according to one senior U.S. intelligence official who briefed reporters on the alleged plot. Authorities said they do not know when the operatives were planning to carry out any of the bombings.

The surveillance, recounted in chilling detail in newly obtained documents, included the location of security desks and cameras in the buildings; traffic and pedestrian patterns surrounding them; employee and vehicle routines; the locations of nearby fire departments, police stations, libraries and schools; and what kinds of explosives would do the most damage to the structures.

U.S. officials said the operatives noted that one of the buildings had three male security guards but that only one carried a weapon. "Getting up to the higher floors is not very difficult if you go there midweek, as I did," one operative added.

The heightened alert, announced by Ridge at 2 p.m., included a level of detail unprecedented in previous warnings. It is the first time that Homeland Security officials have focused the government's color-coded threat system on specific geographic areas. The five earlier orange alerts -- which indicate a high risk of terrorist attack -- were applied to the nation as a whole, most recently on Dec. 31, 2003.

"The quality of this intelligence, based on multiple reporting streams in multiple locations, is rarely seen and it is alarming in both the amount and specificity of the information," Ridge said.

The alert comes as President Bush is under pressure from Democrats and from his opponent, Sen. John F. Kerry (D-Mass.), to show that the government has done everything possible to fend off another terrorist attack. Bush is to announce today his plans for reorganizing the nation's intelligence agencies in response to recent recommendations by the Sept. 11 commission.

In response to Ridge's announcement, authorities in Washington, Newark and New York scrambled to beef up security before government offices and financial markets opened this morning.

New York, which has remained under an orange alert since the Sept. 11 attacks, will host the Republican National Convention Aug. 30 to Sept. 2. Police teams and anti-terror squads will bar trucks from certain bridges, establish checkpoints throughout Manhattan and double security around key office buildings, including the Stock Exchange and Citigroup buildings mentioned in the federal alert. In Newark, heavily armed police set up posts around the 24-story Prudential headquarters.

In the District, police announced plans to stop and inspect cars and trucks around the IMF and World Bank buildings and other sensitive sites downtown, to activate additional surveillance cameras and to flood the areas with foot and car patrols. Authorities indicated that security would be tightened at other facilities, including the White House, Capitol, State Department and U.S. Federal Reserve Board, in case secondary targets were selected.

U.S. intelligence officials' sources of terrorist information are typically more vague and fragmentary. Officials said during briefings with reporters yesterday that the documents related to the latest suspected al Qaeda plot were among the most specific the government had received. But they said they believe that the plans had been in the works for years and contained no specific date for an attack.

In one example of detailed surveillance cited by a senior administration intelligence official, operatives logged the flow of pedestrians outside one targeted building at midday in the middle of a week. "Fourteen persons pass by every minute" on one side of the block, they concluded.

Other communications focused on security barricades, traffic patterns, the use of sewers as escape routes and the locations of nearby fire and police stations, schools and libraries, officials said. For one building, potential attackers discussed how visitors must sign a book telling where they are going, but "on Sunday there is no security. This is not the case on Saturday."

The operatives focused on structural features of the targets that might "prevent the buildings from toppling down," including the thickness of window glass. They discussed separate plans to hijack oil tankers but warned that some contain tracking devices, officials said.

Operatives also intensively monitored employees of the targeted buildings, noting the locations of employee offices in relation to parking garages and identifying local bars and restaurants where employees of the institutions could be met, officials said.

One senior U.S. official likened the new intelligence to a homeowner learning that someone had broken into his house years ago and had been monitoring the occupants all that time.

Such sophistication of planning is a hallmark of al Qaeda. At the U.S. embassy bombings trial in 2001, Jamal Amed al-Fadl, a former associate of Osama bin Laden's, testified that similar surveillance took place four years before the embassies in Kenya and Tanzania were bombed in 1998. Testimony showed that a team arrived in Nairobi in 1994, headed by Ali Mohammed, a former U.S. Army Green Beret now in prison, who had taught surveillance to al Qaeda recruits in Afghanistan training camps.

The team photographed buildings; analyzed access routes, building entrances and guard stations; and kept track of crowd flow around the embassy and other buildings in the area. Surveillance reports were sent to Afghanistan for review by bin Laden and Muhammad Atef, then his chief military planner. Atef, who made one visit to Kenya to review the scene, was killed in November 2001 during a U.S. bombing raid in Afghanistan.

An Aug. 6, 2001, presidential daily briefing obtained by the Sept. 11 commission included a warning about possible surveillance of federal buildings in Manhattan. The FBI has never located the Yemeni man who asked two other Yemenis to take photographs of the buildings.

A White House aide said Bush was informed of the potential threat Friday morning aboard Air Force One by his traveling CIA briefer, during a daily intelligence briefing. At that time, the CIA was still trying to cull the data, and Bush was told about "emerging information that might require us to take preventive action on certain specific targets," the aide said.

The CIA worked round-the-clock on the information for 72 hours before Ridge's announcement, officials said. Members of Bush's Cabinet met about the matter on Saturday and again at 10 a.m. yesterday for more than an hour.

Around noon, Bush authorized Ridge to make the announcement. White House officials said they wanted to make the announcement outside business hours so that workers in the buildings would not panic.

Just before Ridge went on television, Homeland Security officials offered Kerry a classified briefing detailing the intelligence, and the briefing was being scheduled yesterday afternoon, according to the Kerry campaign.

Kerry's senior adviser for national security, Susan Rice, said in a statement yesterday that the heightened alert indicates "we are not as safe as we could or should be" and underscores the need to implement the Sept. 11 panel's recommendations.

"John Kerry and John Edwards will bring all aspects of our nation's power to crush al Qaeda and destroy terrorist networks," Rice said.

Howard Dean, the former Vermont governor and Democratic presidential candidate, also questioned yesterday "how much of this is real and how much of this is politics." He said in an interview on CNN that "every time something happens that's not good for President Bush he plays his trump card, which is terrorism."

Other Democrats, including Sen. Joseph I. Lieberman (D-Conn.), said they did not doubt the credibility of the warning.

"I don't think anybody who has any fairness or is in their right mind would think the president or the secretary of homeland security would raise an alert level and scare people for political reasons," said Lieberman, who also sought the Democratic nomination for president. "That's outrageous."

Ridge said in a conference call with journalists that mayors and governors were notified before yesterday's announcement. He said teams of federal officials met with security officers at the targeted buildings yesterday afternoon.

Ridge indicated that other targets might be part of a al Qaeda plot, but that authorities are still working through the details. "There may be more to come," Ridge said. "We decided not to wait until we were done. We better get out with what we know now."

Staff writers Mike Allen, Juliet Eilperin and Spencer S. Hsu in Washington, and Michael Powell in New York, contributed to this report.

Security was increased around the World Bank in Washington after federal officials named it as a possible al Qaeda target.Police officers from the Hercules Unit patrol the perimeter of the Citigroup Center in New York after authorities warned of a potential terrorist attack. D.C. Mayor Anthony A. Williams talks to reporters during a news conference on possible threats on the International Monetary Fund and World Bank.