Police said, a TSR contingent was fired upon by a group of ultras hiding in a bush at Majhimanipara, near the Indo-Bangla border, about 30 km from Raisyabari police station last evening.
The TSR personnel retaliated and the ultras escaped after a 30-minute encounter.
During a search operation, the TSR team found the bullet-riddled body of an insurgent, two grenades, one AK-47 rifle with 50 live cartridges and receipt of subscriptions.
Police suspect that there were six-seven insurgents in the group which managed to flee to Mayani reserve forest in Chittagong Hill Tract of Bangladesh after the encounter.
The identity of the insurgent is yet to be known.
The police said the ultras were collecting subscriptions forcibly from the villagers.