Thirteen people were killed in violence during the third and final phase of the panchayat polls on Tuesday. More bodies were discovered later.
Tribal groups opposing the rural elections in Rabha Hasong Autonomous Council Areas had clashed with polling officials, the police and non-tribals.
The council is for the Rabhas, a tribal group. They believe the rural polls will make the tribal council powerless.
"The opposition is not committed to decentralisation of power. They were against the rural polls. They instigated and encouraged the rowdy elements involved in Tuesday's incidents. This is evident from the way they are talking on camera after not putting up candidates in the council areas," Gogoi said.
"The violence is slowly taking an ethnic line," said the Congress leader, adding that nearly 100 houses of non-tribals were torched.
Bengali Muslims, Bengali Hindus and Assamese comprise the non-tribals in the tribal council areas.