A supporter of The All India United democratic Front (AIUDF) arrives to attend an election campaign rally in Jaleswar village in Assam, India, March 3, 2016. Photo by Krishna N. Das/Reuters

Gunmen dressed in military gear attacked a Friday market in northeastern India, firing shots and grenades into the crowd and killing at least 13 people and wounding 15 more.

The assault took place in the town of Kokrajhar, located in the country's Assam state. The gunmen pulled up in a van to the busy market before opening fire.

Authorities took out one of the assailants during the attack. The state's police chief Mukesh Sahay told Reuters that he was strapped with explosives and had an AK-4. Authorities were searching for as many as four others in the surrounding area who are believed to have been involved.

"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.

Officials are pinning the violence on a separatist group known as the National Democratic Front of Bodoland, which has carried out attacks in the past.

The Democratic Front represents the Bodo ethnic group. The Bodos have long fought to gain control over part of Assam state, they recently established a council that oversees around 3,000 villages and led by the Bodo People's Front, the BBC reported.

The more militant Democratic Front group has not carried out any large-scale attacks since 2014 when 70 people in total were killed in Assam.