Detectives have arrested four people, including three Chinese nationals, during a drive in the capital's Bashundhara residential area on charges of operating an online fraud network using an illegal SIM gateway.

The arrestees were Jharna Chakma alias Jiana, 27, Liu Hui Zhang, 46, Wei Yuji, 30, and She Yi Ran, 42.

According to the Detective Branch (DB) of Dhaka Metropolitan Police (DMP), the group had  been operating fraudulent activities through online gambling websites from a rented apartment and used around 6,000 SIM cards in the operation.

Briefing reporters at the DMP Media Centre, Additional Commissioner (DB) Mohammad Shafiqul Islam said a DB Cyber Crime team conducted the drive at around 8pm on Saturday based on secret information.

He said the apartment was rented by ethnic community member Jharna Chakma.

The six-storey building was largely rented out to Chinese nationals, with Jharna residing on the ground floor while the remaining floors were occupied by them.

During the operation, detectives found equipment allegedly used for online gateway operations, online gambling and other fraudulent activities.

Police seized 14 laptops, 16 mobile phones, about 6,000 SIM cards of different mobile operators, 20 gateway machines, foreign liquor and Tk 209,700 in cash.

Shafiqul Islam said the suspects used promotional messages offering jobs, discounts or extra income to lure victims into clicking fraudulent links.

He said the gang used the SIM gateway system to facilitate the operation, adding that they recovered around 6,000 SIM cards and SIM slots capable of accommodating approximately 10,000 to 12,000 SIMs.

A single mobile phone was configured to operate with 12 SIM cards for the fraudulent activities, he said.

The DB official said the group changed IMEI numbers of devices through technological means, making them difficult to trace.

He said the network laundered between Tk 200 crore and Tk 250 crore every month through online gambling and other illegal means.

Shafiqul Islam also said many Chinese nationals were carrying out such activities in Bangladesh under the names of different Chinese companies.

He urged people to remain cautious and avoid being lured by fraudulent offers on online platforms, saying such scams were leaving many victims financially devastated.

Police have filed a regular case against the arrestees, he added.