The New York Police is investigating a possible threat of a nuclear attack on the city after an alleged message of an al-Qaeda member was intercepted on the Internet several days ago.

Security measures were tightened across Manhattan, tunnels and bridges, the police installing checkpoints throughout the city in order to scan vehicles with radiation detection equipment.  

The NY police stressed that this report hasn’t been verified and the alert status remains unchanged. Measures taken are precautionary, the city’s mayor Michael Bloomberg saying this is one of the potential threats the police deals with every day and there is no reason to be alarmed “because of this unverified threat” aimed at “spreading fear.”

“These actions are like those that the NYPD takes every day -- precautions against potential but unconfirmed threats that may never materialize,” Bloomberg said.

The turmoil began after a Website posted a report that a message containing threats of an attack with radiological material against New York and other major cities has been circulating on al-Qaeda’s Websites.

Since the September 11, 2001 attacks, New York and other major cities in the United States have remained on the same alert level “orange,” threats appearing frequently without being verified, as mayor Bloomberg said.