The blackmailer had threatened to circulate the schoolboy's video clip online.

Police wrote in a post that the boy was talked into having a video-chat with a stranger online,but did not say whether or not the parents had paid the money. Neither did it say if any arrest was made.

Saying the case was detected by the force's anti-cybercrime Facebook page CyberDefender, police called on parents to remind children to never take off their cloths in video chats or click or download suspicious links as criminal may gain control of the phones remotely.

"Children should never reply to sexually suggestive texts," the force said.

Family Planning Association of Hong Kong encouraged parents to show understanding and seek assistance if their children have fallen victim to "naked chat traps" and suffered from distress instead of blaming them.

"Naked chats" have become common cyber crimes in which fraudsters approach victims on social media and request an online "naked chat" during which they would film the victims.

They then threaten to publish the photos or videos unless the victims buy game point vouchers or cryptocurrencies or pay to designated bank accounts.

The maximum sentences for the crimes are 14 years in jail for blackmailing and eight years and HK$2 million in fine for publishing child pornography.