At least 12 people were killed and 15 others injured Friday after rebels opened fire in a crowded market in Assam state in India's remote northeast, officials said.

Six rebels arrived in a motorized rickshaw and fired automatic weapons and lobbed grenades in the crowded market in Balajan, an area just outside the town of Kokrajhar in western Assam, said top local police official L.R. Bishnoi.

He said that one gunman was killed by security forces and troops were pursuing five others who fled. Several homes and shops were badly damaged in the attack.

Police blamed a faction of the National Democratic Front of Bodoland for the attack. The group has been fighting for an independent homeland for the region's Bodo tribespeople for decades. The Bodos are an indigenous tribe in Assam, making up 10 percent of the state's 33 million people.

Friday's attack was the worst in the recent past, but the group was blamed for the shooting deaths of more than 60 Muslim settlers and Adivasi tribespeople in Assam in separate attacks in 2014.

The rebels have been targeting communities they consider outsiders, including Adivasis, whose ancestors migrated to Assam more than 100 years ago to work on tea plantations — as well as Muslims, accusing them and the federal government of exploiting the region's wealth while neglecting the locals.

Dozens of rebel groups have been fighting the government and sometimes each other for years in seven states in northeast India. They demand greater regional autonomy or independent homelands for the indigenous groups they represent.

At least 10,000 people, most of them civilians, have been killed in Assam state alone in the last three decades.