Police closed several streets in midtown Manhattan (search) and banned trucks from bridges and tunnels leading to the city's financial district Monday following a government warning that terrorists were planning to strike the city.

Despite the warning's unusual specificity, Mayor Michael Bloomberg (search) urged residents to go about their normal business, much as he has done during prior terror warnings.

"Let me assure all of New York one thing," he said at a press conference Sunday. "We are deploying the full array of protection. We will spare no expense.

"Get up tomorrow, go to work and enjoy the freedom terrorists find so threatening."

The terror warning described possible terrorist attacks against financial institutions in New York City, Washington, D.C., and Newark, N.J., saying a confluence of intelligence over the weekend pointed to a car or truck bomb.

The government named the Citigroup buildings and the New York Stock Exchange in New York, the International Monetary Fund and the World Bank buildings in Washington and the Prudential building in Newark as targets.

Beginning Sunday night, police rerouted all Manhattan-bound trucks from the Williamsburg Bridge to the Manhattan Bridge in an effort to streamline random vehicle searches.

Trucks and vans were also forbidden to enter the city through the Brooklyn Battery Tunnel and the Holland Tunnel (search), which lead to lower Manhattan from Brooklyn and New Jersey, respectively. Trucks were instead diverted to the Lincoln Tunnel (search) and the George Washington Bridge (search) in upper Manhattan, police said.

Police also said they would close streets surrounding Grand Central Station, including Vanderbilt Avenue between 42nd and 45th streets and 43rd and 44th streets between Madison and Vanderbilt avenues.

On Sunday, the 59-story Citigroup Center, which has shops on street level and offices above, closed several internal entrances, allowing only workers to enter, and made the shops accessible only from the streets.

A Citigroup official at the building, the third largest in midtown, refused to discuss security there. A company e-mail to employees said they should expect to see tighter security at all its New York buildings.

Streets around the stock exchange, which has been barricaded since Sept. 11, were lightly trafficked except for police and tourists, typical for a Sunday.

"I just pray it (an attack) doesn't happen," Mary Jane Fereza, who was visiting from West Palm Beach, Fla., said from the World Trade Center site, a few blocks away.

Police Commissioner Raymond Kelly said police were advising businesses to safeguard their heating, ventilation and air conditioning systems.

On Sunday night he accompanied police officials from the counterterrorism bureau and the intelligence division to brief the security directors of 13 major financial institutions: Morgan Stanley, Nasdaq, American Stock Exchange, Lehman Bros., Goldman Sachs, Federal Reserve Bank, Bear Stearns, Wachovia, AIG, Citigroup, MetLife, JP Morgan Chase and the New York Stock Exchange. They discussed the recent intelligence reporting about targets in New York and reviewed security measures, a police spokesman said.

In Washington, Department of Homeland Security Secretary Tom Ridge said it would be up to New York officials to decide whether to move to the highest level of security, red. The city has remained a step below, on orange, since the color system was implemented after the attacks of Sept. 11, 2001.

Bloomberg and Kelly said they would not consider placing the city at red alert because the recent intelligence did not indicate when the terrorists might try to attack.