Police armed with rifles and extra patrol cars were stationed around the city, and security was tightened at hotels and landmarks such as the Empire State Building and World Trade Center site. Two police sergeants were stationed in Boston to keep abreast of the intelligence gathering there. Extra officers patrolled houses of worship, police increased bag searches in subway stations and authorities urged residents to be vigilant in a city that has become practiced at wariness since the Sept. 11 attacks.
Although authorities say there have no reports of any specific threats against the city, "The fact is there remain people who want to attack us, and the moment we let our guard down ... is the moment that the terrorists are waiting for," New York City Mayor Michael Bloomberg said.
But while urging caution, the mayor — and his security detail — took the subway to work to show that it's safe, and he urged people to go about their business.
Three people were killed, including an 8-year-old boy, and more than 170 were wounded in the explosions near the finish line of the Boston race Monday.
Since 9/11, the NYPD often has increased security in the city in response to attacks elsewhere, sometimes also dispatching officers to the affected cities. Two New York sergeants went to Boston on Monday night and were working in a regional intelligence center there. Police Commissioner Ray Kelly said wouldn't discuss what they have gleaned about the Boston investigation.
"We believe, and the intelligence community believes, that we're the No. 1 target in this country. So anything we can get to help us better protect the city, we're going to get," he said.
With officials urging New Yorkers to call authorities if they saw anything untoward, scores of them did.
Police responded to 77 reports of suspicious packages in 24 hours, more than three times as many as during the same period last year, Kelly said. Two reports brought out bomb squad officers, but none of the packages turned out to be dangerous, he said.
At LaGuardia, wires protruding from a ceiling spurred a call to authorities and about an hourlong evacuation of the airport's central terminal building, according to the Port Authority of New York and New Jersey, which runs the airport. The wiring turned out to be part of a light fixture.
Around the Financial District, security measures looked the same as they always do, but Bloomberg noted that not all of the precautions being taken would be visible.
Besides undercover officers, the city has invested heavily in security technology, including surveillance cameras, license plate readers and chemical, biological, and radiological sensors. Some 1,000 officers are assigned to counterterrorism work.
Meanwhile, police were re-evaluating security plans for a 5-kilometer run/walk to the National Sept. 11 Memorial and Museum and a 4-mile race in Central Park this weekend, though it wasn't immediately clear whether any rules would change for participants or spectators. And officials are thinking ahead to the massive New York City Marathon next fall, though Bloomberg was quick to stress that officials plan to hold the event after it was canceled last year because of superstorm Sandy.
On Long Island, Nassau County officials planned to meet Wednesday to discuss plans to boost security for the upcoming Long Island Marathon next month. Some says 5,100 runners have signed up for the event, County Executive Edward Mangano said.
He declined to comment on whether officials were considering altering the route, which is largely on the Meadowbrook Parkway.
In New York City, it wasn't clear whether the Boston bombings would become a defining moment in how authorities protect public events in a city already steeped in the protocols of security.
"Our world changed after Sept. 11. The risks have increased — no question about it," Kelly said. "Our position is: Everybody should go about their lives — leave it to the professionals.
"But there are some risks to life these days."