SINGAPORE - If you receive a missed call starting with the numbers '999', do not call back, the Singapore Police Force advised on Wednesday (July 6).

Some members of the public have been receiving unknown missed calls, starting with the numbers '999X XXXX', on their mobile phones, police said in a post on Facebook.

When return calls were made, they reach the 999 police emergency hotline instead.

Police said these calls from unknown origins should be ignored, as "Caller ID spoofing technology may be used to mask the actual phone number and display a different number".

Members of the public can call the police hotline at 1800-255 0000 or submit information online at www.police.gov.sg/iwitness.

They should only dial 999 if urgent police assistance is required, police said.