The 12 civilians were killed and seven wounded on Tuesday in a fresh bout of violence in India's northeastern state of Assam, police said.
Six heavily-armed separatists fired on a group of people gathered in a village square in western Assam before escaping into the jungle, said Dhubri district police chief L R Bishnoi.
Ten people - all from the Muslim minority - died on the spot, the officer said.
"The condition of at least three of the injured is very critical," he said, adding that security forces were hunting for the attackers, who he said used "sophisticated weapons."
Security forces in north-east face
upto two dozen rebel groups
It was the fourth attack in the district since Sunday, blamed on rebels belonging to the outlawed National Democratic Front of Bodoland.
The latest attack took the death toll in recent days in the northeast to 81 with a further 217 injured. The region has around two dozen anti-government and separatist groups.
The National Democratic Front of Bodoland is fighting for an independent homeland for the Bodo tribe and is active in parts of western and northern Assam.
In other violence in Dhubri early on Tuesday, rebels killed a villager belonging to the rival Adivasi Santhal community while army soldiers shot dead a rebel from the United Liberation Front of Asom (ULFA) in eastern Assam.
The United States meanwhile has offered to help probe the attacks, saying officers from the Federal Bureau of Investigation could be made available to help hunt down the attackers, according to the external affairs ministry in Delhi.
Thousands have died in separatist
revolt in Kashmir since 1989
In Srinagar, the summer capital of Indian-administered Kashmir, at least three Indian army soldiers were killed when separatists opened fire on them late on Tuesday evening on the outskirts of the city, police said.
The encounter began at around 7.30 pm (1400 GMT) when the separatists opened fire on a group of troops in the Zainakote locality of the city.
Three soldiers died on the spot and the area cordoned off, police said.
Additional forces were being sent to the area as more details were awaited.
More than 40,000 people have been killed since an Islamic separatist revolt erupted in Indian-administered Kashmir in 1989, according to official figures. Separatists put the toll between 80,000 and 100,000.