If you're walking along the streets of an historic part of Tampa, Florida, Big Brother is not only watching you but also scanning your face to see if it matches with a known criminal.

The Tampa Police Department has installed face-recognition software in 36 closed-circuit television (CCTV) cameras in Ybor City, an entertainment district in downtown Tampa that is popular with locals and tourists. Tampa is the first US city where the police use this technology for routine surveillance.

Visionics of Jersey City has offered the Tampa police use of the FaceIt software free for a year in an effort to build a market among municipalities.

The closed-circuit televisions were installed in 1997 to help police officers scan the crowds, said Detective Bill Todd of the Tampa Police Department. The cameras were linked to the FaceIt software on June 29th.

"We had an opportunity to evaluate it from the manufacturer," he said. After one year, it would cost the police $30,000 (€33,079) to buy the software.

The police believe Ybor city is a good place to try out the system because it has the same crime rate as Tampa overall but has more muggings and bag snatchings because it draws such large crowds.

Currently, the police are only using the face-scanning software on weekends - Thursday, Friday and Saturday nights - when the streets are closed off and there are large crowds milling around.

So far, however, he said, they have had no luck catching anyone, but he remains optimistic that the face-scanning software will help them arrest felons and prevent crimes.

The police department has placed signs in Ybor City that warn: "Smart CCTV is in use."

The cameras scan faces and compare them to photographs of 30,000 runaways, murderers and wanted criminals held in a database in the police control room. The system works by analysing 80 facial points around the nose, cheekbones and eyes. If 12 reference points are the same, the software signals that a match has been found.

At that point, a system operator would determine if the images were similar enough to radio an uniformed police officer who would investigate and possibly make an arrest.

If an image is not found in the database, the scanning system immediately dumps the image.

In the middle of July, about 100 people wearing masks and making obscene gestures demonstrated against the police cameras installed on the streets of Ybor City.

But several police departments here and overseas continue to buy the software.

Virginia Beach is seeking a $150,000 state grant for a similar system and several law-enforcement agencies throughout the US have installed FaceIt to put people's mugshots into their criminal justice systems.

Since 1998, the FaceIt system has been in use in London's Newham borough where, in association with the Metropolitan Police Service, 300 cameras are tied into the CCTV control room.

Ms Frances Zelazny, director of corporate communications at Visionics, says Newham is the only place the system has been installed long enough to see how effectively it works. After one year, she says, "police saw a 40 per cent reduction in crime".

This prompted a visit by British Prime Minister Tony Blair and Home Secretary Jack Straw who announced the nationwide expansion of the CCTV initiative to identify juvenile delinquents.

In April, Birmingham city centre integrated FaceIt technology into its CCTV system, as part of Operation Safer Streets.

The West Midlands police are hoping it will help combat street crime across the region.

In June, Keflavik International Airport in Iceland introduced FaceIt to survey passengers entering Iceland from the European Union.

The Keflavik airport police hope it will assist them to identify known criminals and false asylum-seekers.

In Australia, the New South Wales Police Department is using FaceIt to create, archive, search, retrieve and share digital photographs and criminal history records.

The FaceIt technology is also used in casino applications and in combating football hooliganism.

Besides facial-recognition technology, Visionics sells fingerprint software to help book criminals at the time of arrest and to vet job applicants, Ms Zelazny says. There is "significant interest" in facial-recognition technology, she adds.

Visionics has 300 partners who have adopted the technology or are in the process of developing products that use facial recognition.