The existence of such a search program was disclosed Thursday by US News and World Report's website. That report said the US government has a secret program to monitor homes, workplaces and mosques of Muslims in at least six cities for signs of nuclear radiation.

Up to 120 Muslim sites in the Washington area, and more in New York, Chicago, Seattle, Detroit and Las Vegas, have been regularly monitored for radiation for more than three years over concerns about nuclear terrorism following the September 11, 2001 attacks, US News reported.

"Government agencies (had) disclosed that they have installed radiation-detection equipment at ports, subway stations and other public locations, but extensive surreptitious monitoring of private property has not been publicly known," the Times noted.

The Times said the US federal government has given thousands of radiation alarms, worn like cellphones on the belt, to police and fire departments in major cities.

It quoted a spokesman for the Justice Department, Brian Roehrkasse, as confirming that law enforcement personnel were conducting "passive operations in publicly accessible areas to detect the presence of radiological materials, in a manner that protects US constitutional rights."

President George W. Bush's administration has been criticized over revelations that government agencies -- including the National Security Agency, the Department of Defense, and the FBI -- spied on US citizens without first obtaining court orders as mandated by law.

Bush, who authorized the NSA surveillance, maintains that the spying is legal and that he has the legal authority to permit such activities.

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