Police sealed off some streets in New York, put international-finance employees in Washington through extra security checks, and added barricades and a heavy armed presence in Newark, N.J., in response to a heightened terrorism alert aimed specifically at titans of the financial sector.

Treasury Secretary John Snow, quick to try to reassure investors and Americans generally, said the nation's financial system operated normally in the first weekday hours of the code-orange alert.

"People around the world rightly have confidence in the U.S. financial markets," Snow said. "While we must always remain vigilant against terror, we will not be intimidated and prevented from enjoying our lives and exercising our freedoms."

Police checked identity cards as employees filed in to the World Bank headquarters, and guards at its sister institution across the street, the International Monetary Fund, swept the underside of cars with detecting devices as they entered the garage.

Police were more visible, although not in large numbers, in a capital that has already fortified key buildings against terrorism. "I'm concerned but we have to carry on as normal," said Shirley Davies of Britain, who has worked at the IMF for seven years. The bank and the fund are among largest employers in Washington, with more than 10,000 people in both buildings, two blocks from the White House.

Along with the international institutions, authorities placed the Citigroup Center building in New York, the New York Stock Exchange and Prudential Financial Inc.'s headquarters in Newark, N.J., under heavy scrutiny after unusually detailed information identified those buildings as terrorism targets, and prompted the government to raise its terrorism alert.

New York police closed several streets in midtown Manhattan and banned trucks from bridges and tunnels leading to Wall Street. Mayor Michael Bloomberg and Gov. George Pataki rang the opening bell at the stock exchange in a show of confidence in the city's precautions.

In Newark, Prudential employees threaded through police and concrete barriers into their offices. "I'm a little nervous given the 9/11 situation, but I'm confident Prudential's doing everything they can to ensure our safety," said Tracy Swistak, 27, an analyst in the international finance department.

A heavy contingent of authorities checked identification and bags at the 59-story Citigroup Center, midtown Manhattan's third largest building.

"It's definitely a scary building to be working in when we're a big target," said Chip Persons, 35, who works on the 24th floor.

Officials acted on intelligence that Homeland Security Secretary Tom Ridge called alarmingly specific, but he said officials could not tell whether an attack might be imminent and he encouraged people to go about their business.

"We have to go on being America," he said on ABC's "Good Morning America." "We can't button up and be what we're not."

A cache of recently obtained information -- including photos, drawings and written documents -- indicates that al-Qaeda operatives have undertaken meticulous preparations to case the five specific buildings.