UPDATE: NYC Stepping Up Security Amid New Terror Threat

After Thursday's report that Al Qaeda was planning a vehicle-based attack in either New York City or Washington, DC around the 9/11 anniversary, both cities are stepping up security.

The threat, first reported Thursday night, comes from CIA-gathered intelligence which suggests a credible plan has been hatched to use a vehicle or vehicles to blow up targets in one of the cities hit by the 9/11 attacks ten years ago. Three men are believed to be involved in the plot, including one U.S. citizen. All three men are believed to be in the country.

The attacks are alleged to be Al Qaeda's response to the killing of Osama Bin Laden by American Special Forces this spring. The plan appears to be to use the 9/11 remembrance as a trigger for the event, amplifying whatever damage can be wrought by the attacks.

In New York, New York City Mayor Michael Bloomberg is not taking the threats lightly, even though they have not been confirmed as of yet.

"We have to not let the terrorists win by intimidation," said Bloomberg.

Still, he called on all new Yorkers to be alert over the weekend, as the 9/11 anniversary remembrances begin to take place.

"Over the next few days we should all keep our eyes wide open," said Mayor Bloomberg.

"For ten years we have not allowed terrorists to intimidate us," Bloomberg said. "There is no reason for any of the rest of us to change our daily routines. Over the past ten years, [the NYPD] has helped thwart over a dozen potential attacks. The best thing we can do to fight terrorists is to refuse to be intimidated by it."

Accordingly, New York City Police Commissioner Ray Kelly announced several measures his department is undertaking to beef up security ahead of the anniversary. His department is extending each shift by four hours (essentially adding 1/3 to the police force presence in the city) and setting up vehicle search points, bomb dogs, and radiation detectors at various points throughout the city.

"The public is likely to see and maybe somewhat inconvenienced by vehicle check points at various locations throughout the city," said Kelly.

In Washington, the President has ordered the intelligence community to do what it must to track and neutralize the threat, if possible.

In a statement, Department of Homeland Security spokesman Matthew Chandler said, "As we know from the intelligence gathered from the Osama bin Laden raid, al Qaeda has shown an interest in important dates and anniversaries, such as 9/11. In this instance, it's accurate that there is specific, credible but unconfirmed threat information."

"As we always do before important dates like the anniversary of 9/11, we will undoubtedly get more reporting in the coming days," said Chandler. "Sometimes this reporting is credible and warrants intense focus, other times it lacks credibility and is highly unlikely to be reflective of real plots underway. Regardless, we take all threat reporting seriously, and we have taken, and will continue to take, all steps necessary to mitigate any threats that arise."