The blast occurred near a temporary election office of BJP in Assam's Goalpara.
One of the injured in the powerful bomb blast near BJP office at Dudhnoi in lower Assam's Goalpara district succumbed to his wounds at a Guwahati Hospital, raising the death toll to three.
The man who was shifted to the Gauhati Medical College Hospital after suffering injuries in the explosion, died today, a senior police officer said.
Two persons, including All Assam Bengali Yubo Chatra Federation's Goalpara district President Bapan Saha, were killed and 21 others, including four police men, were injured in the blast triggered by suspected ULFA(I) activists near a temporary BJP election office.
The bomb was suspected to have been kept in a bag on the footpath near the BJP office, adjacent to Dudhnoi traffic police point.
Meanwhile, ULFA (Independent) has denied its involvement in the blast claiming "it was trigerred by those political parties who apprehended the large voter turnout would go against their pre-poll calculations".
The segment would go to the hustings in the second phase of assembly polling on April 11.
The polling time was incident-free in the state on Monday with a record of over 80 per cent voter turnout in the first phase of polling in 65 of the 126 Assembly segments.
Goalpara Election district is among the 61 constituencies going to the hustings in the second phase on April 11.