US authorities are investigating a credible but unconfirmed threat that al-Qaeda plan attacks on New York and Washington to coincide with the 10th anniversary of the September 11 assaults.
Police are hunting three people who may have recently entered the country.
Michael Bloomberg is the mayor of New York City:
“As we approach the tenth anniversary of the 9/11 attacks, the NYPD, FBI and the entire intelligence community have been on heightened alert because we know that terrorists view the anniversary as an opportunity to strike again. Now, the threat at this moment has not been corroborated. I want to stress that. It is credible but it has not been corroborated, but we do live in a world where we must take these threats seriously and we certainly will. “
Security has been tightened across the US in the build up to the anniversary, but there are no plans to change President Obama’s travel schedule for Sunday’s commemorations.
The president is due to mark the day with a visit to ground zero, the Pentagon and Shanksville Pa. He will later attend a memorial concert at the Kennedy Centre in Washington.