The five, of Pakistani descent and aged 19 to 35, include four Hong Kong ID card holders and one who is in the city on a “going-out pass” - a recognizance form for overstayers.

They were arrested for robbery between Tuesday and Saturday.

Of the five, a 28-year-old suspect has been charged with one count of the offense and will appear in the Kowloon City Magistrates’ Court tomorrow.

And the rest have been released on bail and should report back to the police early next month.

All the suspects, with businessmen, security guards and jobless individuals among them, were plotters of the robbery, lookouts and getaway drivers respectively, police said.

Yau Tsim District Crime Unit inspector Fu Ho-sing said earlier, the 39-year-old South Korean man, also a restaurant manager, agreed to help a crypto buyer he befriended online settle a Bitcoin transaction.

In return, he was promised a commission of several thousand dollars.

At around 6 pm on July 28, the victim withdrew HK$3.29 million cash belonging to the buyer from a Tsim Sha Tsui crypto company on Ashley Road, before heading for the nearby Astoria Building to meet the seller.

At 6.22 pm, he ascended the building’s stairs instead of taking an elevator up as the buyer told, since the elevator had broken down.

Shortly afterwards, the victim was besieged by four of the suspects - about 180-centimeter tall each and wearing dark clothes, with one threatening him with a 12-centimeter beef knife.

In response, he shielded himself using his right hand, during which his right palm was slashed.

The four suspects then tied the victim to the stairs’ handrail, after which they snatched the HK$3.29 million cash from his backpack and another HK$10,000 cash of his own from his satchel respectively.

At 6.30 pm, the suspects fled in a white Toyota Mark X car towards the direction of Kowloon Park, after which the victim successfully untied himself and reported to the police.

Later, the injured victim was sent to the Queen Elizabeth Hospital in Yau Ma Tei conscious.

Meanwhile, police retrieved the car the suspects boarded from a Hing Wah Street West parking lot in Sham Shui Po, believing the suspects dispersed from the spot.

Fu said the design and plotting of the robbery was “highly precise”.

He also said police were hunting for three more relevant suspects, and appealed to witnesses to come forward with information.

“Police appeal to those who witnessed activities happening around Kowloon Park Drive or the Hing Wah Street West parking lot to contact the police as soon as possible,” he said.

Fu reminded citizens not to carry out large transactions alone, but rather had friends or companions to keep them company.

"Combating crimes related to earning quick money has been one of the police commissioner’s priorities, and police will pursue each of them relentlessly,” he said.