NEW YORK, Dec 24: In search of a terrorist nuclear bomb, the US government since 9/11 has run a far-reaching, top secret program to monitor radiation levels at over 100 Muslim sites in the Washington DC area, including mosques, homes, businesses and warehouses, plus similar sites in at least five other cities, The US News and World Report magazine said in a report.

The magazine said that in numerous cases, the monitoring required investigators to go to the property under surveillance, although no search warrants or court orders were ever obtained, according to those with knowledge of the programme.

Some participants were threatened with loss of their jobs when they questioned legality of the operation, according to these accounts.

Federal officials familiar with the programme maintain that warrants are not needed for the kind of radiation sampling the operation entails, but some legal scholars disagree.

News of the programme comes in the wake of revelations last week that after 9/11, President Bush approved electronic surveillance of US targets by the National Security Agency without court orders.

These and other developments suggest that the US government’s domestic spying programmes since 9/11 had been far broader than previously thought, the report said.

It said that the nuclear surveillance programme began in early 2002 and had been run by the FBI and the Department of Energy’s Nuclear Emergency Support Team (Nest).

Two individuals, who declined to be named because the programme is highly classified, spoke to US News because of their concerns about legality of the programme.

At its peak, they say, the effort involved three vehicles in Washington DC, monitoring 120 sites per day, nearly all of them Muslim targets drawn up by the FBI.

For some 10 months, officials conducted daily monitoring and resumed daily checks during periods of high threat.

The programme has also operated in at least five other cities when threat levels there have risen: Chicago, Detroit, Las Vegas, New York and Seattle.

FBI officials expressed concern that discussion of the programme would expose sensitive methods used in counter-terrorism.

Although Nest staffers have demonstrated their techniques on national television as recently as October, US News has omitted details of how the monitoring is conducted.

Officials from four different agencies declined to respond on the record about the classified programme: the FBI, Energy Department, Justice Department and National Security Council.

“We don’t ever comment on deployments,” said Bryan Wilkes, a spokesman for Department of Energy’s National Nuclear Security Administration, which manages Nest.

In Washington, the sites monitored have included prominent mosques and office buildings in suburban Maryland and Virginia.