SINGAPORE - Letters signed by a 'Lord Voldemort' have been sent to Yishun residents recently, and the police have advised the public not to respond to the letter writer.

According to the police advisory, the sender had asked members of the public to inform a resident of the block to pay up, or he would harass the units there.

Lord Voldemort is a reference to the villain in author J. K. Rowling's popular Harry Potter novels.

In a Facebook post by Nee Soon GRC MP Lee Bee Wah on Wednesday (Aug 30), she said that the police have put up an advisory at the notice board and have stepped up patrols.

"All residents, if you see suspicious characters loitering or harassing units, please take photos and videos of them and submit them to the police," she wrote.

The police said they have received at least 15 reports of such cases from multiple locations. They advised the public not to follow the sender's instruction and not to send any e-mail replies to the sender's e-mail address.

"Instead, please lodge a police report and hand over the letters to the police," said the police.