US intelligence officials said they have detected a potential terrorist plot timed to coincide with the tenth anniversary of the September 11 attacks
Security is to be heightened in New York City and Washington DC, after a "specific, credible but unconfirmed" threat was discovered, according to a statement issued by the Department of Homeland Security.
Officials believe the alleged plot was initiated by the new al-Qaeda chief, Ayman al-Zawahiri, who pledged to avenge the death of Osama bin Laden earlier this year.
Mayor Bloomberg addresses the people of New York after receiving threats. He offered people assurances by stating that he would travel by subway himself
Janice Fedarcyk, FBI Assistant Special Agent, said, "al-Qaeda has shown an interest in important dates and anniversaries. In this instance it is accurate that there is credible, specific but unconfirmed information."
President Barack Obama was briefed on the information earlier and requested that counterterrorism officials step up their response to the suspected threat, according to White House spokesmen.
It is understood that three people who recently entered the country, one of them a US citizen, are urgently being investigated by security officials over a potential plot to detonate vehicle bombs, possibly on bridges or tunnels.
Notes seized in the US raid on the Pakistani hideout of Osama bin Laden, the former al-Qaeda leader, in May, indicated that the terrorist network had discussed the possibility of attacks to coincide with Sunday's anniversary. A strike against American trains was suggested.
Reports indicated the suggestion of a threat may have come from the Pakistani border regions, where known al-Qaeda and Taliban operatives are based.
Raymond Kelly, the New York police commissioner, said vehicle checkpoints would be set up around the city, and that police would place "increased focus" on the city's bridges and tunnels.
People tie 'Ribbon of Remembrance' on The Bell of Hope, which rings once a year on September 11 to remember victims from the 9/11 attacks, at St Paul's Chapel near Ground Zero
More random bag checks would take place on public transport, he said.
Alongside Kelly, Michael Bloomberg, the Mayor of New York City, said, "The best thing we can do to fight terror is to not let it intimidate us." '
He said he would be taking a Subway train to work. "I can tell you our ceremonies will go on over the weekend exactly as they were planned."
The suspected threat came as America prepared to mark the anniversary of 9/11 with a series of events commemorating the nearly 3,000 people who died when hijackers crashed planes into the World Trade Centre in New York, the Pentagon, and a field in rural Pennsylvania.
Sarkozy pays his respects French President Nicolas Sarkozy said yesterday he remembers being dumbstruck at seeing TV images of the 9/11 attacks on the World Trade Center, and still keeps a small steel block retrieved from the twin towers rubble in his office as a reminder.
"On this day of September 11, every French person felt hit," Sarkozy said. "The barbarians chose New York as the epicenter, but it could have been Paris."
92% Number of men in Afghanistan who said they were unaware of 9/11 after being read three paragraphs of the attacks and the consequences of the attacks