Members of the United People's Democratic Front (UPDF) and the JSS (Santu Larma) group are locked in an armed battle in Rangamati's Baghaichhari upazila.
Baghaichhari Police Station Officer-in-Charge (OC) Shahadat Hossain confirmed the development.
The JSS led by Santu Larma is the group with which the government signed the CHT Peace Accord of 1997. The UPDF came into being a year later with an official position expressing 'skepticism' of the accord, and advocating full autonomy.
According to the locals, the gunfight started on Sunday evening and continued at high intensity for about 45 minutes, in which both sides exchanged approximately 350 to 400 rounds of bullets.
Intermittent gunshots are still being heard till the filing of this report.
The sound of the gunshots created panic among the people of the area. However, no casualties were reported.
Three firing incidents happened at the same place in the last month.
Meanwhile, the UPDF coordinator of the Sajek region, Argent Chakma, said some 30 to 35 armed cadres of JSS started firing on UPDF activists suddenly, but then fled when UPDF responded.
Trideep Chakma, a leader of the JSS Santu Larma party, could not be reached for comments on the incident despite several attempts.
Read more: UPDF man gunned down in Rangamati