The syndicate rented a 3,000 square feet two-story apartment in Sha Tin with a swimming pool, drove a Porsche and other luxury cars, and hired a chauffeur, according to the police.

Acting police superintendent Benjamin Tai Tze-bun of the cyber-security and technology crime bureau said yesterday that 154 men and one woman all aged between 18 to 43 were scammed between last January and April this year, involving a total loss of more than HK$21 million.

In the two-day operation launched on Monday, 10 men and five women, aged between 22 to 70, were arrested at the Sha Tin house and two industrial building units in Cheung Sha Wan and Lai Chi Kok, including the mastermind and 11 core members.

Chief inspector of the bureau Cheng Chak-yan, said the suspect moved to the apartment last April for a monthly rent of HK$70,000, which was also their headquarter. Several surveillance cameras were installed inside and outside the apartment for monitoring.

He said the syndicate was led by the younger son aged 43; his girlfriend and elder brother were responsible for luring victims, manipulating puppet bank accounts and renting units, while the mother was in charge of accounts.

The police found that they mainly targeted local men. Members posed as people from different countries or as Hongkongers working abroad, to lure victims on social media and to make them fall in love with them.

They made up fake stories, claiming that they were facing financial difficulties or using other excuses to demand money.

Tai said victims never met their "lovers" throughout the process and did not know they had been defrauded until they lost their money. One of the largest losses involved HK$1 million.

Some victims were instructed to assist in money laundering and that they could receive handling fees after transferring the money.

The police seized two recreational vehicles, three laptops, 23 mobile phones, HK$300,000 in cash, two watches worth a total of about HK$1.5 million.

"If a new online friend asks for money transactions or provides personal information, or uses your own personal account to transfer money, you should always be cautious and alert to avoid becoming a target of fraudsters," Tai said.