WASHINGTON – The federal government raised the terror alert level Sunday to “orange” for the financial services sectors in New York City, Washington and Newark, N.J., citing the discovery of remarkably detailed intelligence showing that al-Qaida 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 pointed to five potential targets: the International Monetary Fund and World Bank headquarters in Washington; the New York Stock Exchange and Citicorp Center in New York; and the Prudential Financial building in Newark, N.J.

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

In Maine, Gov. John Baldacci said there is no reason for alarm at the warnings.

But even though the announcements include no threats against sites in Maine or New England, he said they give him and other state officials the chance to reaffirm how important it is for all Maine’s residents to remain alert for terror risks.

“It’s better to be safe than sorry,” Baldacci said. “We have more protective measures in place than ever before and we will maintain our vigilance and resolve as a state.”

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 various 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 of the operatives added.

The heightened alert, announced by Ridge publicly at 2 p.m., included a level of detail unprecedented in previous warnings and marks the first time 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, have been applied to the nation as a whole, most recently on Dec. 31, 2003.

“The quality of this intelligence, based on mutiple 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 also comes as President Bush is under daily pressure from Democrats and from his opponent, Sen. John Kerry, D-Mass., to show that the government has done everything possible to fend off another terrorist attack. Bush plans to announce Monday his plans for reorganizing the nation’s intelligence agencies in response to recommendations by the Sept. 11 commission.

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

In New York, which has remained under an “orange alert” since the Sept. 11 attacks and which will host the Republican National Convention later this month, police teams and anti-terror squads will bar trucks from certain New York bridges, establish checkpoints throughout Manhattan and double security around key office buildings, including the New York Stock Exchange and Citicorp buildings mentioned in the federal alert. In Newark, heavily armed police set up posts around the 21-story Prudential headquarters.

And in the District of Columbia, 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 also indicated that security would be tightened at other facilities in case secondary targets were selected, including the White House, U.S. Capitol, State Department and U.S. Federal Reserve Board.

U.S. intelligence officials – whose sources of terrorist information are typically more vague and fragmentary – said during briefings with reporters Sunday that the documents related to the latest al-Qaida plot were among the most specific the government had ever received. But they acknowledged 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 of the targeted buildings 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, the 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,” and discussed separate plans to hijack oil tankers but warned that some contain tracking devices.

They also intensively monitored the 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.

“It’s as if someone long ago broke into your house and now you realize he’s been monitoring everything you did for years,” one senior U.S. official said.

Such sophistication of planning is a hallmark of al-Qaida. At the U.S. embassy bombings trial in 2001, Jamal Amed al-Fadl, a former associate of Osama bin Laden, testified that similar surveillance took place four years before the U.S. 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-Qaida recruits in Afghanistan training camps.

The team photographed buildings, analyzed access routes, building entrances, guard stations and kept track of crowd flow around the embassy and other buildings in the area. The surveillance reports were sent back 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. But 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 first informed of the potential threat Friday morning aboard Air Force One by his traveling CIA briefer, during his 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 around 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. Sunday 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 building 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 Sunday afternoon, according to the Kerry campaign.

Kerry’s national security advisor, Susan Rice, said in a statement Sunday 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.