Guwahati: Attackers wearing military uniforms shot dead at least 13 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.

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

One assailant was killed and security forces were in pursuit of three or four others hiding in a nearby forest, Assam police chief Mukesh Sahay told reporters.

Sahay said police had recovered an AK-47 rifle and explosives from the dead gunman, as well as a three-wheeler van the assailants had arrived in.

He blamed the outlawed National Democratic Front of Bodoland (Songbijit) group, a militant outfit fighting for a separate homeland for the indigenous Bodo tribespeople. The dead gunman was yet to be identified, said Sahay.

A senior home ministry official in New Delhi said preliminary reports indicated the attack, one of the deadliest in recent years in a region with a history of sectarian and separatist bloodshed, was carried out by the group.

‘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, has suffered from years of ethnic and tribal insurgencies. Prime Minister Narendra Modi's nationalist Bharatiya Janata Party (BJP) won power in a state election in May for the first time after pledging to increase spending in the state.

‘This attack is intended to destabilise peace in Assam,’ said Himanta Biswa Sarma, the state's finance and health minister and a member of the BJP. There was no claim of responsibility for the attack.

Violence in Assam and the wider northeast has fallen as more militant groups have called ceasefires, although attacks by one community against another are not uncommon.

Militants fighting for a Bodo homeland killed at least 70 people, most of them tea-plantation workers from other parts of India, in a series of attacks in Assam in late 2014.