Tanzanian police are still searching for billionaire Mohammed Dewji, 43, after masked gunmen abducted him outside a swanky hotel gym in the commercial capital, Dar es Salaam, on Thursday morning.
Police believe two of his abductors were white men, but the identities of the 12 who were arrested by the end of Thursday have not been made public.
Police have not given any further update on their investigations.
Mr Dewji, locally known as Mo, is described by financial magazine Forbes as Africa’s youngest billionaire.
It estimates that he is worth $1.5bn (£980m).
He is the CEO of MeTL, a family empire started by his father in 1970’s of which Mo is credited with turning it from a wholesale and retail enterprise into a multi-billion dollar pan-African conglomerate.
Authorities are yet to establish the motive for the kidnapping.