Also known as an "advance fee" or "419" scheme, the scammers sent spam e-mails asking for help in transferring a large sum of money out of a politically or economically troubled country, in exchange for a generous percentage.

Robert Meulenbroek, spokesman for the Amsterdam prosecutor's office, said the ring broken this week had reaped millions of euros (dollars). Recent victims included people from the United States, Japan, England, Russia, Sweden and Switzerland.

A task force of 80 officers raided 23 apartments, seizing computers, fake passports and euro50,000 ($62,000) in cash. One suspect was injured attempting to escape by leaping from a third-floor apartment, he said.

The detainees were not identified under Dutch privacy rules, but most were believed to be Nigerian, police said.

In a variation on one of the world's oldest scams, the Nigerian e-mail con presents himself as a well-connected person who needs access to a Western bank account to transfer a large sum of money that cannot be spent in his own country.

He promises a cut of the money in exchange for a smaller upfront cost before the larger sum can be transferred -- but it never is.

The scam has existed for years in various forms, but in the 1990s it moved online, where it is cheaper to organize and harder to trace.

Arrests have been made in several countries in recent years, including Australia, Canada, and the United States.

The Amsterdam scammers referred their potential victims to Web sites of fictitious companies with names like Global Securities and Financial Company Limited, or Fortune Trust Finance & Securities.

Often, they listed a fake address, though most had a working mobile phone number.

The suspects worked from their homes and sent more than 1 million e-mails, at times clogging the servers of their Internet provider, Dutch-based cable company UPC. Police enlisted UPC's help to trace them, Meulenbroek said.

Six people, three from Nigeria and three from Benin, were convicted in a similar case in Amsterdam in May, receiving sentences of up to 4 1/2 years. They had defrauded victims for several million dollars (euros), including a Swiss professor who lost US$482,000 after being promised 25 percent of a US$36 million sum.

Nigeria has recently stepped up its efforts to eradicate the scam, which taints its image abroad. The Central Bank of Nigeria denies any connection to the scammers, and Nigerian agencies have been placing warning advertisements in international newspapers for years.

The scam is sometimes called a "419" fraud due to the Nigerian criminal code outlawing it.

At the World Economic Forum in Davos, Switzerland earlier this month, Nigeria's finance minister, Ngozi Okonjo-Iweala, reissued a statement promising to crack down on the scammers.