Of the four who were rescued from a prayer hall, two sustained serious injuries in the assault at Boithamari village under Kamalabari police station.
Majuli Sub-divisional Officer Loya Maduri said local people tied the four, brought to the prayer hall ('namghar') and beat them up to make them confess that they practised witchcraft.
Local administration managed to defuse the situation and shifted the injured to Jorhat Medical College Hospital.
The situation was tense in the island and strict vigil was being maintained to prevent further such incidents.