Some elderly people have been pressurised into handing over their life savings to the operators of a lottery scam.
The new Jamaican-based lottery scam has already seen some people in the UK lose several thousand pounds, the Office of Fair Trading (OFT) said.
Victims received phone calls from operators claiming to be lawyers, bank officials or lottery organisers.
But then they were told they needed to pay fees to release lottery “winnings”.
Further calls demanded more money, and in some cases people have been threatened with violence, arrest and removal to Jamaica if they did not pay up.
The scam has already targeted people in other countries and an estimated $30m (£18.5m) has been lost in the US.
Law enforcement agencies said that victims’ money ended up in the hands of organised gangs and helped to fund other serious crime in Jamaica.
“We know that Jamaican-based lottery fraudsters have actively targeted US consumers in the past, but we are now beginning to see this emerge as a problem in the UK,” said Heather Clayton of the OFT.
“What is despicable is that some victims have been threatened with violence to coerce them into handing over their life savings.
“A genuine lottery would never ask someone to pay taxes, insurance or any other fee before receiving their ‘winnings’.”
Paul Evans, from the Serious Organised Crime Agency, said: “There is no doubt that there are links between mass marketing fraud and other serious organised criminality, including drugs importation and threats of violence.”
In one case, a 79-year-old woman from Warwickshire received calls threatening deportation if she failed to pay processing fees to receive a £2.5m lottery “prize”. She paid £3,150 before calling the police.