Attackers wearing military uniforms shot dead 12 people and wounded 15 on Friday in a busy market area in a town in India's restive northeastern state of Assam, in an attack blamed by the authorities on a regional separatist group.

Three or four gunmen fired indiscriminately and threw hand grenades at the crowded market in Kokrajhar, a town about 220 km (137 miles) west of the state's commercial capital Guwahati, eyewitnesses said.

One assailant was killed and security forces were in hot pursuit of three or four others in the area, Assam police chief Mukesh Sahay told TV channel CNN News 18.

A senior home ministry official in New Delhi said preliminary reports indicated the attack was carried out by separatist militants of the National Democratic Front of Bodoland (Songbijit).

"Police have launched a hunt to trace insurgents hiding near the incident spot. It is a militant attack and we will be sending a team from Delhi to investigate further," the official said.

Assam, a remote and underdeveloped state in India's northeast, has suffered from years of ethnic and tribal insurgencies. Prime Minister Narendra Modi's nationalist party recently won power in a state election.

"This attack is intended to destabilise peace in Assam," said Himanta Biswa Sarma, the state's finance and health minister. There was no claim of responsibility for the attack. - Reuters