At least six people have been killed by a bomb in Guwahati, the main city in the Indian state of Assam, police say.
A victim of Friday's attack in Guwahati (Photo: S Bhattacharjee)
The blast, in the busy Machkhowa market, also injured at least 13 on Friday afternoon.
Later, three explosions rocked the oil town of Naharkatiya and a grenade was thrown at the home of a politician.
Police say they suspect rebels of the United Liberation Front of Assam (Ulfa) are behind the attacks. The rebels have denied involvement.
Rebels have been fighting for independence since 1979 in a struggle which has claimed 10,000 lives.
Officials say three people died immediately in Friday's blast. Two others died on the way to hospital and one died in the hospital.
Overnight, one person was killed and 30 others injured in four separate explosions elsewhere in Assam.
Police say Thursday's attacks were carried out by unidentified men who threw grenades in four towns, striking markets and a police station.
The police said the explosions happened in Nowgaon, Golakganj, Dhubri and Mongoldoi areas between 2100 and 0200 local time (1530-2030 GMT Thursday).
Assam police intelligence chief Khagen Sarmah told the BBC that separatist rebels belonging to the Ulfa group were active in the area where the overnight blasts took place.
"Though there is no evidence yet that the Ulfa was involved, the needle of suspicion points to them," he said.
The rebel group has denied any involvement in the explosions.
"Those who want the peace dialogue in Assam scuttled are using mercenaries to stage such attacks so that we can be blamed," Ulfa military wing chief Paresh Barua told the BBC.
Ulfa is currently holding peace negotiations with the Indian government through a committee of civil society leaders called the People's Consultative Group (PCG).
The PCG has twice met Indian government officials but Ulfa has yet to announce a formal ceasefire, although it says it wants an end to military operations in Assam.
The federal government informed the group on Friday that the next round of talks will be held in the Indian capital Delhi on 22 June.