Gauhati: Suspected insurgents lobbed a hand grenade at thousands of people participating in a cultural festival on Sunday in India’s troubled northeast, killing three and wounding another 50, police said.

Nearly 15,000 people belonging to the Mising tribe were participating in the festival when the blast went off, said Diwakar Mishra, the top district administrator.

Fourteen seriously injured people were taken to a hospital in the nearby town of Dibrugarh, Mishra said.

Police blamed the blast on the United Liberation Front of Asom, a separatist group that has been fighting for an independent homeland in the area for more than two decades.

Mishra said the attack in Jonai, a town 600 kilometers (375 miles) north of Gauhati, the capital of Assam state, came as the rebel group observed its Army Day,’ commemorating the date it set up its armed wing in 1981.

Several rebel groups are fighting for autonomy or independence in India’s northeast. The militants say India’s national government exploits the region’s rich natural resources while doing little for the area’s indigenous people.