US treasury department has sanctioned Chinese-born Cambodian tycoon Chen Zhi – alleged mastermind of a cyber-crime empire in south-east Asia

The UK and the United States have sanctioned a multinational network based in south-east Asia accused of running large-scale online scam operations that are suspected of using trafficked workers to defraud people around the world.

The industry has flourished in recent years, especially in parts of Cambodia and Myanmar where hundreds of thousands of people have been duped by false job adverts and then forced to commit online fraud, including through romance scams, sometimes under the threat of torture.

The US treasury department said it had taken what it described as the largest action ever in south-east Asia, targeting 146 people connected to the Prince Group, which the UK also sanctioned.

Those sanctioned include the head of the Prince group, Chen Zhi, as well as more than a dozen individuals connected to his business operations across south-east Asia and the Pacific.