Pranab Boro, 45, poured petrol and set himself on fire before the state secretariat during an agitation organised by Krishak Mukti Sangram Samiti (KMSS).
"Doctors tried to save his life. Boro died at 4:28 pm. He suffered 100 per cent burn injuries," Hospital Superintendent Ramen Talukdar told PTI here.
The immolation, a first among Assam's farmers, sparked widespread protests and road and rail blockades in various parts of the state.
The National Highway-37 was blocked at numerous places, including at Koliapani in Jorhat district and Gaurisagar in Sivasagar district with the police picking up 10 protesters.
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The police detained another 50 KMSS activists from Jorhat, Golaghat and Guwahati.
Protests were also reported from Morigaon and Sonitpur districts where railway tracks were blocked.
The KMSS had organised the protest in view to disrupt a government programme to distribute land ownership certificates at the Sankardeva Kalakshetra here.