An increase in police enforcement against loan sharks in recent years has helped reduce the number of harassment cases by these unlicensed moneylenders.

Police received just under 9,000 reports of loan-shark harassment last year, down from 11,776 cases in 2011 and 15,525 in 2010.

These include instances where loan-shark runners scribble debtors' notes on the walls of Housing Board flats or splash paint on the doors of residents.

But it seems the tough enforcement action has driven loan sharks to resort to new ways of harassing members of the public in recent weeks, some of whom may not even have borrowed money from them.

About two weeks ago, Mr Frankie Nge returned home from work only to receive a letter threatening to harm him if he did not pay up for a "loan".

The note was sealed in an envelope with his home address written on it and deposited in his mailbox.

It was handwritten in both Chinese and English, with photos of a corpse and cars splashed with paint. The note ended with "Don't report to (the) police" because "we can trace you".

The 37-year-old construction engineer told The Sunday Times that he had not taken any loans from illegal moneylenders. So the next morning, he reported the matter to the police.

Mr Nge, it seems, was not the only one who had received such threats, said the police last Friday.

A spokesman said the police have observed an ongoing trend of such threats made to members of the public, despite efforts in raising public awareness on illegal loanshark activities.

Besides these anonymous letters, the police have also received reports on similar threats made through phone calls and text messages, said Deputy Superintendent of Police Madeline Low.

"Preliminary investigations indicate that in many of these cases, the victims supposedly did not borrow money from the loan sharks, but nevertheless received those threatening calls and SMSes," said DSP Low.

The public is advised to report such scams to the police immediately instead of contacting the caller or the sender of the text messages.

They should also not give in to their demands to transfer any money or repay the loan.

DSP Low added: "Do not disclose your personal particulars to the caller or sender such as your name, NRIC number, residential address, contact details and any other confidential information."