Victims of impersonation scams involving fake China officials lost at least $5.3 million from January to May, the police said in a statement yesterday.
The police received 92 reports of such scams during the period.
The ruses usually involved someone impersonating an officer from a government organisation or staff member from a courier company.
The victims would be told that their mobile phone numbers had been used in a crime or that parcels bearing their names had been found to contain illegal goods.
Some victims were told that there were pending court cases against them.
The scammers would get the victims to provide their personal particulars or bank account details, including Internet banking credentials and one-time passwords, for "investigation" purposes.
The victims would later discover that money had been transferred from their bank accounts to other unknown accounts.
Sometimes, the calls would be transferred to other people who would identify themselves as police officers from China.
Victims might also be shown copies of warrants for their arrest from the Chinese police and be threatened with imprisonment if they refused to cooperate.
In another ruse, the scammers would instruct their victims to scan QR codes and transfer money using bitcoin-vending machines.
Victims might also be asked to withdraw money from their bank accounts to be handed over to a "government officer" for verification.
The scammers would keep the victims on the phone to ensure that they could not verify the authenticity of the call.
The police have advised the public not to believe the person at the other end of the line if they receive unsolicited calls from unknown numbers.
Recipients of such calls should not give any identification or personal details and should try to remain calm throughout the call, the police said.