"Over a hundred tea garden workers hacked Ujjal Hajam to death. Local tea garden workers suspected Ujjal of practicing black magic due to which many girls turned mentally sick," a police official said.
He said that another youth Manmohan Bocca, who assisted Ujjal, managed to flee when the mob attacked them on Thursday night.
The police official said Ujjal's father Shibsankar Hajam filed a case in the local Laxmipur police station against the assailants.
The practice of branding people, mostly women, as witches and torturing them continues in remote, rural and tribal areas of Assam, Tripura and other north-eastern states.
In the last few years, more than 50 people, mostly women, have been tortured and beaten to death on suspicion of practising witchcraft or black magic in Tripura.