Bradford investors have been fleeced for thousands of pounds in an elaborate scam exploiting people's fear of global terrorism.

Fraud police warned people to be aware of the con in which victims are urged to invest in US security-based companies currently booming because of the 'War on Terror'.

The bogus brokers rent tiny offices - often broom cupboard-sized spaces next to the boiler room - within prestigious financial complexes in cities such as Zurich and Geneva to give them an illusion of respectability.

The 'boiler room' fraudsters also launch websites featuring photos of plush headquarters and profiles of executives which are simply copied from legitimate firms' own sites. They even create false links on existing business websites where would-be investors can read fake articles about the bogus firm.

The conmen then ring potential victims offering a 'get rich quick' investment which they need to snap up immediately or miss out.

These typically involve low-priced stock from small US firms, often centring on products booming through the 'War on Terror'.

One area often used is biometrics, a hi-tech industry featuring James Bond-style products where the eye is scanned to allow access to secure areas.

Investors later discover their stocks are worthless and can then be scammed for a second time by others firms promising to recover their losses at a cost.

Detective Chief Inspector Dave Cooper, who heads West Yorkshire Police's Economic Crime Unit (ECU), formerly known as the Fraud Squad, said: "We have had victims who have parted with quite a lot of money - a six-figure sum in one case."

One West Yorkshire victim, who lost a five-figure sum, said: "I received a telephone call out of the blue and then another person came back to me on the phone asking if I was interested.

"They directed me to their website and I downloaded loads of information to check it all out, but what I didn't realise was it had all been faked. They had an answer for every issue I raised, and they made it sound so attractive that I thought 'Why not?'"

Detective Constable David Parker, of the ECU, said: "We encourage investors to thoroughly investigate any investment opportunity and the person promoting it before parting with any money, especially if they are investing with an overseas broker who is not regulated by the UK's Financial Services Authority (FSA).

"The best way to protect against this type of investment fraud is to independently check references and not to reply to sophisticated company websites that are often spoofed.

"When investing in a foreign country, contact the local or national regulatory authority that has jurisdiction for that area."

He added: "Investors could also contact an FSA-regulated UK broker to help them in evaluating the merits and risks involved."