At least 10 people have been killed, most of them civilians. Police say Ajit Mahanta, the man whose death kicked off the protests, was suspected of membership in the United Liberation Front of Assam.
Sonia Gandhi, the head of the Congress Party, visited Assam and said members of the security forces who needlessly killed civilians should be punished severely, the Indian Express reported.
"I am pained at the incidents and have already taken up the matter with the defense minister and stressed on exemplary punishment to the erring security personnel," Gandhi told Congress supporters at a rally.
Assam, in northeastern India at the foot of the Himalayas, is one of a group of provinces connected to the rest of the country only by a narrow strip of land and has international borders with Bangladesh and Bhutan. Groups seeking greater self-government have been active since the 1980s.