Police in a joint operation detained at least 63 foreign nationals for their suspected involvement in online gambling activities in the West Jalalabad area of the city on Thursday night.

The Counter-Terrorism Unit and Khulshi Police Station conducted the operation at an eight-storey building in the area, said Mohammad Faisal Ahmmed, additional commissioner (Crime) of Chattogram Metropolitan Police (CMP).

He, however, declined to provide details of the operation.

According to preliminary police information, the detainees included 35 nationals from Laos, 21 from Pakistan, five from China, one each from Nepal and Vietnam.

Of the 63 detainees, 41 are men, 21 women and one is a child.

Police said 131 mobile phones and 170 laptops were seized from the building. Foreign currencies and casino gaming equipment were also recovered.

Local residents said they noticed frequent movement of foreign nationals in and out of the building for about a month. However, they said they were unaware of the activities being carried out inside.

Police suspect the building may have been rented for operating a casino or conducting online gambling activities.

However, the exact nature of the activities and the purpose of the foreigners' stay are still being investigated.