Online fraudsters scammed Hong Kongers out of more than HK$200 (870 million baht) in a week last month and used artificial intelligence (AI) to trick a victim into transferring HK$145 million in one of the cases.
Police said the victim, a merchant, wanted to buy cryptocurrency mining equipment used to create digital tokens.
The purchase was negotiated via the WhatsApp messaging app with what the victim thought was a mainland Chinese company.
"During the negotiations, the merchant received what seemed to be WhatsApp voice messages from the financial manager of the company," police said.
"Following the instructions, the victim transferred about HK$145 million worth of USDT cryptocurrency into a designated cryptocurrency wallet, three times in total."
The victim later realised the transactions were part of a scam and filed a police report.
USDT, or Tether, is a type of digital currency that is pegged to the US dollar.
Police said an investigation found that the real financial manager of the mainland company had accessed a bogus WhatsApp page on a laptop.
"Fraudsters are likely to have compromised the WhatsApp account, using AI to mimic the financial manager's voice for the scam," the force said.
The case was the largest in terms of funds lost between Jan 20 and 26. The largest single amount in online shopping scams was HK$1.5 million.
At the end of last month, Commissioner of Police Raymond Siu Chak-yee urged residents to be on guard against investment scams and fraudsters who impersonated mainland officials, amid a recent rise in such cases.
"In the past one to two months, we have seen an increase in the number of investment scams," the police chief said during a Lunar New Year visit to Che Kung Temple in Sha Tin last week.
"We see that scammers start with online romance schemes, showing concern for your well-being at first. Afterwards, they send you a link. They may also offer some sweeteners to entice victims and make them believe they can make money."
The force issued alerts on its CyberDefender social media page in recent days and said 42 residents had fallen victim to online romance scams with combined losses of more than HK$30 million in the past two weeks.
In one of the alerts issued on Wednesday last week, police said that a property owner was cheated out of HK$7 million in cryptocurrency.
According to police, the woman put her flat up for rent on a real estate platform. She later received a WhatsApp message from a stranger who claimed to be interested in renting the property.
"They got along well, and the man even sent her trainers and a scarf, hoping to show some warmth," police said.
"At this point, the woman was fully invested in the relationship, but the man suddenly said he wasn't interested in renting the property."
The force said the man claimed to be an investment expert and convinced the woman to put money into cryptocurrency on a bogus trading platform called Coinupex.
The victim ended up transferring more than HK$7 million across multiple payments to the scammer's cryptocurrency wallet.
The fraudster vanished after receiving the funds.
"Wake up! Be vigilant. Even when scammers give gifts, they are just trying to get more money from you," police said.
The force urged the public to be vigilant over such scams during the coming Spring Lantern Festival, also known as Chinese Valentine's Day, on Wednesday and Valentine's Day on Friday.
Residents were also advised to use the force's Scameter search engine, which is accessible through the CyberDefender website and available as an app, to check suspicious or fraudulent links.