The US government has seized more than $14bn (?10.5bn) in bitcoin and charged the founder of a Cambodian business empire, the Prince Group, with allegedly masterminding a massive cryptocurrency scam, which involved forced labour camps.

UK and Cambodian national Chen Zhi was charged on Tuesday in New York for allegedly engaging in a wire-fraud conspiracy and money laundering scheme.

Mr Chen's businesses were also sanctioned by the US and the UK as part of a joint operation. The UK government says it has frozen assets owned by his network, including 19 properties in London - one of which is worth nearly ?100m ($133m).

The BBC has contacted the Prince Group for comment.

US prosecutors said it was one the biggest financial takedowns in history and the largest ever seizure of bitcoin, with approximately 127,271 bitcoin being held by US government.

Mr Chen, who remains at large, is accused of being the mastermind behind a "sprawling cyber-fraud empire" operating under his multi-national company, the Prince Group, said the US Department of Justice (DOJ).

The Cambodia-based group's website says its businesses include property development, and financial and consumer services. But the DOJ alleges that it runs one of Asia's largest transnational criminal organisations.

Unwitting victims were contacted online and convinced to transfer cryptocurrency based on false promises that the funds would be invested and generate profits, the DOJ said.

Prosecutors alleged that the company, under Mr Chen's direction, built and operated at least ten scam compounds throughout Cambodia, according to court documents seen by the BBC.

Mr Chen was accused of managing the compounds that were specially designed to reach as many victims as possible, said prosecutors.

His accomplices allegedly procured millions of mobile phone numbers and set up "phone farms" to conduct call centre scams, according to the court documents, dated 8 October.

Two of these facilities had 1,250 mobile phones that controlled around 76,000 social media accounts for scams, the documents said.

Prosecutors said Prince Group documents included tips on building rapport with victims, advising workers not to use profile photos of women who were "too beautiful" so that the accounts would look more genuine.

Assistant Attorney General for National Security John A Eisenberg described the Prince Group as a "criminal enterprise built on human suffering".

It also trafficked workers, who were confined in prison-like compounds and forced to carry out scams online, targeting thousands of victims worldwide, he said.

Mr Chen and his accomplices allegedly used the criminal proceeds for luxury travel and entertainment, said the DOJ.

They also made "extravagant" purchases like watches, private jets and rare artwork, including a Picasso painting purchased from a New York City auction house, the department said.

If convicted, Mr Chen faces a maximum penalty of 40 years in jail.

In Britain, Mr Chen and his accomplices allegedly incorporated businesses in the British Virgin Islands and invested in UK property. His network's assets include a ?100m office building on central London, a ?12m mansion in North London and seventeen flats in the city, said the UK foreign office on Tuesday.

Being sanctioned, as part of a joint operation with US authorities, means he is now locked out of the UK's financial system.

The Prince Group has also been sanctioned in the US and labelled as a criminal organisation.

They were "ruining the lives of vulnerable people and buying up London homes to store their money", UK Foreign Secretary Yvette Cooper said.

Cooper said: "Together with our US allies, we are taking decisive action to combat the growing transnational threat posed by this network - upholding human rights, protecting British nationals and keeping dirty money off our streets."

The foreign office said Mr Chen and the Prince Group built casinos and compounds used as scam centres and laundered the proceeds.

Four businesses linked to the alleged scams - The Prince Group, Jin Bei Group, Golden Fortune Resorts World and Byex Exchange - have also been sanctioned, said the foreign office.

Two scam centres allegedly run by Jin Bei Group and Golden Fortune Resorts were named earlier this year in an Amnesty International report on the use of forced labour and torture in Cambodian scam centres.

People working in scam centres are often foreign nationals lured by the promise of a legitimate job, and then forced to carry out scams under threat of torture, the foreign office said.

These scammers operate on an "industrial scale", including in the UK, using tricks like fake romantic relationships to lure victims into being scammed, said the foreign office.

Fraud Minister Lord Hanson said: "Fraudsters prey on the most vulnerable by stealing life savings, ruining trust, and devastating lives. We will not tolerate this." (BBC)

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