Only days before the tenth anniversary of the 9/11 attacks, the United States is under a new terrorist threat.
In a hastily called news conference late Thursday, New York Mayor Michael Bloomberg warned of “unconfirmed” intelligence that a terrorist attack was being planned to mark the tenth anniversary of 9/11.
"We know the terrorists regard the anniversary as an opportunity to strike again. We do live in a world where we must take these threats seriously," Bloomberg said.
Although details of the threat are vague, ABC news said intelligence agencies received information that three people had entered the U.S. with the intention of staging a "vehicle-borne" attack on the anniversary of September 11.
Officials believe the suspected attackers began their journey in Afghanistan and may have passed through Iran.
It’s believed that New York or Washington, D.C. are the intended targets with bridges and tunnels the most likely places where an attack could be launched.
Officials say any unattended car left near an infrastructure in NYC or D.C. will be towed.
The threat -- believed to be in the form of a single piece of intelligence -- was first received on Wednesday night. President Obama and key intelligence personnel were first briefed on Thursday morning.
“The president directed the counterterrorism community to redouble its efforts in response to this credible but unconfirmed information," a White House official told Fox News.
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Another senior U.S. official with knowledge of the threat said it was "specific enough to elicit worry."
New York and Washington, D.C. will especially see heightened security for the next several days -- at least through Monday, the day after the 9/11 anniversary.
New York’s police chief Ray Kelly said he has ordered increased bag checks on the subway, a 30% increase in police patrols and rapid response teams, added deployment of officers specializing in detecting nuclear radiation and extra sweeps at religious and government buildings.
There will also be exercises involving several security agencies at Grand Central, Penn station and Times Square on Friday.
Mayor Bloomberg said that the NYPD was also well prepared, having helped to thwart at least 12 possible terror attacks since 9/11.
Bloomberg urged people to be vigilant but defiant. "The best thing we can do to fight terror is to refuse to be intimidated by it. For the past 10 years we have not allowed terrorists to intimidate us, we have lived our lives without fear and we will continue to do so."
Bloomberg said he intends to take the subway to work Friday -- as usual.
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