Troops patrolled the streets in Nagaland state to prevent further bloodshed, while the bombings continued in western Assam state.
The violence across the two states was some of the deadliest to hit the ethnic patchwork region, where more than three dozen insurgent groups have been active - including one of Asia's longest running separatist conflicts, dating to shortly before India gained independence from Britain in 1947.
In Sunday's deadliest attacks, a bomb exploded in the evening near a market in Bijni, 125 miles west of Gauhati, the capital of Assam, killing three people.
Shortly afterward, another explosion killed another man and wounded 25 in nearby Gauripur along India's border with Bangladesh.
In the same region, a bomb went off a tea plantation in Borhat village, killing a worker and wounded two others, Press Trust of India news agency said.
And two suspected rebels of the outlawed National Democratic Front of Bodoland were killed when explosives they were carrying detonated in Assam's Sonitpur district, PTI said.
Federal Home Minister Shivraj Patil visited Assam and Nagaland on Sunday to assess the violence, which began Saturday when suspected separatists detonated a bomb at a packed railway station and sprayed gunfire into bustling markets. At least 50 people were killed in attacks Saturday.
No group claimed responsibility and it wasn't clear whether the nine attacks in Nagaland and Assam states were linked.
But Inspector-General Khagen Sarma, the top police official of Assam state, told The Associated Press he "cannot rule out" the possible involvement of the outlawed National Democratic Front of Boroland, a tribal separatist group that is active in the region.
Sunday is the 18th anniversary of the group, which is demanding a homeland for Boroland, a region that straddles both states. On Friday, Assam Chief Minister Tarun Gogoi, the state's top elected official, offered a truce to the Boroland rebels and the region's largest insurgent group - the United Liberation front of Assam - beginning Oct. 16 if they accepted a cease-fire.
Nagaland has also been the scene of an insurgency that has killed 15,000 people since Naga rebels began fighting for a separate nation nearly six decades ago. The rebels want special status for Nagaland state, which borders Myanmar and where most of the 2 million Nagas - most Christians - live in predominantly Hindu India.
In other attacks Sunday in Assam state, a bomb went off in a market in Dhekiagula village, north of the capital, wounding 15 people, police said.
Rebels also hit a natural gas pipeline with a land mine near Borhat in western Assam, a police officer said on condition of anonymity. The extent of the damage was unknown.
Another bomb exploded at a shop in Dabosal in western Assam, wounding its owner, said A.K. Bhutani, the district magistrate. And in the nearby town of Chitra, suspected militants blew up an electrical transmission tower, snapping the power supply to the area, Bhutani said.