Three Africans have been arrested on suspicion of being part of a gang that traffics women from Africa into prostitution in Bangkok.

Officials from the Department of Special Investigation (DSI) first detained a man from Mali, identified only as Baba, in Nong Khai province. Two Tanzanian women, identified as Lulu and Zuwena, were later arrested in Bangkok on Monday.

The arrests were part on an ongoing operation by the Ministry of Justice and the DSI targeting human trafficking networks in Thailand.

The gang members called themselves "madam". Their job was to supply and force African women into the sex trade, working in entertainment venues on Sukhumvit road.

The gang collected the money the women earned from customers and forced them to pay for their travel themselves. The traffickers used "black magic" superstitions to control the women, police said. 

The investigation is continuing.