The suspected National Liberation Front of Tripura (NLFT) militants issued the threat though a telephone call to the Vanglaini newspaper, Mizoram's most widely circulated daily, on Thursday.
The caller identified himself as Lalduhawma, a known Bru outlaw who intelligence officers say has been on their radar for years.
He said he was calling on behalf of the "Bru Democratic Front of Mizoram". Top sources however said there is no such outfit and suspected it to merely be an alibi for the NLFT, a tribal militant group which has for decades been targeting "Bengali settlers" in Tripura.
Sources described Lalduhawma as someone who has been associated with various armed gangs that emerged after the two main Bru militant groups - Bru National Liberation Front and Bru Liberation Front of Mizoram - laid down their arms after peace deals with the Mizoram government in the last decade.
These include the Bru National Development Liberation Front of Mizoram (BNDLFM), which was later changed to Western Development Liberation Front of Mizoram (WDLFM), believed to be involved in the current kidnapping.
Besides having lived in various western Mizoram villages, Lalduhawma is said to have mainly resided in the Naisingpara Bru relief camp in Tripura, the largest of six such camps.
He is suspected to be linked with militants who looted Rs 198 lakhs from the Zawlnuam BDO office in Mizoram's Mamit district last July, and part of which was believed to have been handed over to NLFT cadres in exchange for firearms and assistance.
The kidnapped men are Deep Mandal, an employee of Noida-based Telecom Network Solutions who was working on a contract for Airtel, and two Mizo drivers Sanglianthanga and Lalzamliana.