A 39-year-old Hong Kong man was kidnapped last week and held for ransom after agreeing to meet a Tether cryptocurrency buyer in Hong Kong's Kowloon Bay, The Standard reported Monday.

The man was taken inside an industrial building, where he was assaulted and forced to hand over his phone and trading platform passwords.

The crypto trader managed a daring escape after being tortured with a hammer and suffering many fractures to his wrists and legs.

Between last Friday and Sunday, a group of seven people, including a woman, were detained for kidnapping the victim and demanding HK$30 million in ransom from his family.

Last Friday, the victim, who had several fractures in his arms and legs, escaped through a window of a metal shack in Nam Hang Tsuen rural village in northern Tai Po. He was brought to the hospital and underwent his second surgery on Sunday night, according to reports.

The victim was forced to hand over his information to his online banking account and bitcoin trading sites by the kidnappers. They requested that he contact his relatives and friends for ransom by pretending to be in debt to them.

The kidnappers demanded HK$8 million at first, but the ransom was eventually raised to HK$30 million. Authorities said the victim's family did not pay the ransom.

A private car was used to carry the victim to an unknown container terminal on November 7 at midnight. He was later transferred to a metal shack in Nam Hang Tsuen about midnight on November 8.

The next day, the victim's family went to the police station. On November 10, police began their investigation and discovered the victim's whereabouts.

On Saturday and Sunday, five more kidnappers were arrested after further investigations. A few weeks before, the victim is reported to have made a transaction with one of the kidnappers.

Police added that all seven are members of the renowned Sun Yee On Triad, and are between 25 and 32.

Two of the seven claimed to work in the transportation industry, one in the catering industry, and one in the auto detailing industry. The other three stated that they were unemployed.

Alan Chung Nga-lun, senior deputy superintendent of the Kowloon West regional criminal unit, said the force seeks the mastermind and other kidnappers involved.

"We've noticed an increase in cryptocurrency transactions. Meanwhile, some gangsters fabricate numerous justifications for requesting a face-to-face transaction," Chung said in quotes by The Standard.