Brazilian police said Thursday they had seized gold bars, luxury watches, piles of cash and other bling in a crackdown on a group accused of mounting an international, multi-million-dollar pyramid scheme using fake cryptocurrency investments.

The group is accused of swindling thousands of investors in Brazil, the United States and at least 10 other countries by convincing them to "rent" cryptocurrency assets, allegedly offering returns of up to 20 percent a month, federal police said in a statement.

In reality, "while part of the money was used to make the monthly payments, the rest was used to acquire high-value real estate, luxury cars, boats, designer clothes, jewels and other items" for the suspects themselves, police said.

The crackdown, which involved around 100 police officers, came after the US Department of Homeland Security tipped Brazilian authorities off to a multi-million-dollar money-laundering case involving a cryptocurrency Ponzi scheme based out of Brazil.

The group is accused of moving up to four billion reais ($770 million) in Brazil alone over the course of six years.

The scheme's alleged mastermind -- dubbed the "Bitcoin Sheik" in the press -- was based in the city of Curitiba, in southern Brazil, where he claimed to have assembled a large team of crypto traders.

The group, which included many of his family members, also sold its own supposed cryptocurrencies, promising extravagant monthly returns, police said.

Brazilian media reports said victims included football players and a famous TV presenter's daughter.

Police dubbed the sting Operation Poyais, after a fictional Central American land invented by infamous 19th-century Scottish swindler Gregor MacGregor.

MacGregor's scam helped trigger a stock market crash in 1825 by cheating British and French investors hoping to make a fortune in the New World out of the equivalent of some $5 billion in today's money.