New Terrorist Threat Looms Only Days Before 9/11 Anniversary

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.

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.