At least 1,500 people were defrauded
Spanish police have arrested 87 Nigerians suspected of defrauding at least 1,500 people in a postal and internet lottery scam.
The arrests were made in and around Madrid in an operation co-ordinated with the FBI.
Police said millions of euros were taken from the victims, most of them in the United States and European Union.
Those targeted were wrongly told they had won a lottery and asked to send a payment before prize money could sent.
Thousands of letters and e-mails, most in ungrammatical English, were sent out to prospective victims every day, police said.
The faked documents asked them to make an initial payment of 900 euros ($1,400, £720) in taxes or administrative costs.
The scam is estimated to have netted around 20 million euros, but the actual sum could be many times that, say police.
Police said the number of those defrauded could run into many thousands, as most of them probably failed to report the crime out of embarrassment.
Police estimate that only one in 1,000 recipients of the letters needed to fall for the fraud for it to make a profit. An Anglican bishop was among those duped, according to Spanish officials.
The operation to track down the gang began in May 2007 when a huge number of identical letters destined for addresses in the US was discovered at Madrid's Barajas airport.
Police confiscated hundreds of computers, mobile phones and 60,000 letters in a raid on more than 30 homes and businesses.
Law enforcement officers also seized a suitcase full of fake $100 notes which they say was used to convince some victims who came to Spain in person to collect their "prize money".