Police on Friday said they believe they are getting closer to the alleged perpetrators connected to the unlicensed cryptocurrency exchange JPEX, after arresting another four men in a joint operation with Macau police.

The force said they arrested two men, both 28, while the Macau police arrested two men aged 29 earlier this week.

They said they seized or froze HK$24 million in assets in the operation – including casino chips, luxury watches and gold bars.

Assistant police commissioner Eve Chung refused to disclose the roles of the four, but described them as "rather important".

"The persons we arrested this time, or those that we're after now, play a rather important role in the scam network," she said, adding that the force is deploying the entire crime wing and the "super computer" to probe the case.

"Some of them are not in Hong Kong right now, and so we will use international cooperation mechanisms, including police cooperation and other legal means, to bring them to justice."

Chief superintendent Kelly Cheng said there are different hurdles to overcome due to the complexity of the case.

"For this case, it involves thousands of e-wallets and tens of thousands of transactions. And also because of the anonymity of the cryptocurrency in the cyber world, it makes it quite difficult to identify the criminal behind," she said.

"That's why we have been keeping liaison with the overseas virtual assets trading platforms. So we will make every effort to hunt down the syndicate and also trace the cryptocurrency and the crime proceeds."

So far, 2,417 people have complained about losing money on JPEX, involving a total of over HK$1.5 billion.