The 45-year-old Pranab Boro doused himself in petrol and set himself on fire before the state secretariat during an agitation organised by Krishak Mukti Sangram Samiti (KMSS).
Boro was admitted to the Gauhati Medical College Hospital with 100 per cent burn injuries, hospital superintendent Dr Ramen Talukdar said.
As soon as news of Boro's bid spread, protests erupted at various places across 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.
Thousands of protesters gathered before DC offices in Jorhat, Tinsukia and Sivasagar districts and shouted slogans against the state government.