The operation was jointly carried out with Interpol and police in Malaysia, where another seven people were arrested.
The police alleged that the suspects used online platforms to chat to their victims, who were asked to pay money for business investments or customs clearance fees for gifts.
The three men and 17 women arrested in Hong Kong are aged between 20 and 66. They were granted police bail pending further investigation.
“The biggest amount of money involved in one case was HK$1.8 million, the victim is a 29-year-old investment manager. He dated a suspect on an online platform, they discussed some investment proposals, and he fell into this fraudulent trap,” said chief inspector Cheung Wai-ho from the police’s cyber security and technology crime bureau.
The force said mobile phones, bank cards and documents were seized in the operation and there could be further arrests.