People are asked to transfer cash at bureaus

In one case, a 74-year-old woman was duped into sending more than �200,000 to a conman who told her she had won a prize draw in Las Vegas.

Victims are typically told by letter or telephone they have had a big lottery win but have to pay a fee to get it.

Police say the scams are conning people in the UK out of �1 billion a year.

Internet auction sites have contributed to the increase in fraud, BBC crime correspondent Neil Bennett reports.

People are persuaded to send payments through the money transfer system, which involves going into a money bureau and handing over cash.

Neither the goods bid for or the lottery wins ever materialise.

The police are warning the public to wire money only to people they know and trust.