Unofficial sources said Rs a ransom 30 lakh were paid by relatives of those abducted but it cannot be confirmed by the police.
The police said they received the information late as the relatives were dealing directly over phone with the abductors who kept the hostages inside a jungle in Bangladesh.
Sapan Kumar Roy (52) of Dosda Bazar in North Tripura district, his driver Govinda Nath (35) of Dharmanagar in North Tripura district and Sankar Nath (35) of Rangamati in Assam's Karimganj district were abducted at gun-point by five people at around 8 PM on November 25.
The three came at the BSF camp in Rajiv Nagar on Wednesday night after their release, the sources said.
Police suspected that the three persons were abducted by the NLFT or the newly-formed Borok National Council of Tripura (BNCT) militants.