MTR bosses are warning the public over a possible scam involving con-artists posing as the railway company and sending out free tickets by mail.

The firm said on Wednesday that it was alerted to the suspected scam by reports on social media that some people had received complimentary annual passes and were asked to scan a QR code on the back to activate them.

The company said it had not sent out such items in recent days and would not ask people to activate a pass using a QR code.

It said it has reported the matter to the police.