Thousands of fake cheques worth some £8m ($16.2m) have been seized in an attack on international e-mail scams.
Cheques: Seized in Nigeria
The cheques, offered as prizes in exchange for a fee and destined for the UK, were recovered in Nigeria by the Serious Organised Crime Agency (Soca).
The month-long investigation into the fraud uncovered more than 4,500 forged and fraudulent documents.
UK officials are working with agencies in the US, the Netherlands, Canada and Spain to tackle "mass marketing fraud".
A handful of people have been arrested in the UK with almost 70 more held overseas.
Online dating fraud
The operation was launched to tackle the growing problem of people being conned through this type of fraudulent activity, which comes in a variety of different ways such as e-mail, letter or telephone.
Soca said the investigation work being done in Nigeria is "one part of a sustained and ongoing law enforcement response to mass marketing fraud".
DESTINATION OF FAKE CHEQUES AND POSTAL ORDERS
South East: 343
South West: 14
East Anglia: 3
West Midlands: 131
North East: 148
North West: 842
Such scams are thought to cost the UK up to £3.5bn a year and are growing because of abuse of the internet and mobile phones.
They include such scams as people being offered cash or prizes in exchange for a fee, as well as men being conned out of thousands of pounds by fraudsters on dating websites.
Mike Haley, head of consumer protection at the Office of Fair Trading, told BBC One's Breakfast programme those using dating websites were easy prey because of their reluctance to report the fraud.
"Most people are embarrassed to admit they have got involved in such a scam. It shows the very sophisticated ways fraudsters use."
Criminals demand money from dating website customers after masquerading as a fellow user in order to build up a relationship of trust, he said.
"They say something like they have been sick and they need some money to go to hospital, or there has been an accident in the family."
Stephen Day, from Ipswich, handed over sums of money totalling £12,000 to someone he met online. The woman he thought he was emailing and sending money to for flights and other expenses turned out to be a Nigerian man.
"It is not easy to admit that you have been subject to this sort of scam. It is almost something that you feel ashamed of.
"It was totally unprepared to be drawn into what was quite extensive international financial fraud from an internet dating site."
Parag Bhargava, a founding member of the Association of British Introduction Agencies, called for more stringent checks of dating sites.
"What we would like is some kind of legislation that suggests that if a person is joining such a site that some sort of verification checks are made about the actual individual."
One of the most well-known frauds is an email offering a share of a huge windfall of cash in return for a fee needed to unlock the account where it is being held.
Scams campaign: Launched by Nigerian authorities
These con tricks - known as 419 scams - are run by well-organised criminal gangs based abroad working on the basis that enough people will be conned to make it worth while sending thousands of messages.
The fake cheques and postal orders seized were to be sent to addresses throughout the UK with most of them targeting people in London.
In each case the crime gang would have already received a fee from the intended recipient. Fake passports and other documents were also recovered, said Soca.
Agencies from the US, UK, Netherlands , Nigeria, Spain and Canada have been co-ordinating efforts because neither all the victims nor the perpetrators live in one country.
The partnership has identified thousands of bank accounts used in the frauds, according to officials.
'High volume' crime
Soca said police in London are continuing "operational activity" following the Nigeria-based operation.
Home Secretary Jacqui Smith said: "This type of fraud is a despicable crime that is costing UK victims huge sums of money every year, many of whom are elderly or vulnerable, and causing emotional and financial harm to them and their families.
"I completely support the significant effort being led by the Serious Organised Crime Agency to raise public awareness of this crime and in building stronger international relations to bring these offenders to justice."
Paul Evans, a Soca director, said international co-operation had been key to the operation with "unrelenting" commitment from Nigerian investigators.
"Mass marketing fraud is a low value, high volume crime," he said. "Relatively small amounts of money quickly add up to big profits for the fraudsters.
"Organised criminals respect no borders and international cooperation is vital when tackling this type of fraud."