"A tense situation is prevailing... Police and security forces are jointly patrolling, hopefully, peace will restored soon," said Ahsan Habib, deputy inspector general at Chittagong Range Police.
The Bengali man's lynching triggered retaliatory attacks on ethnic minority communities, officials said.
Dozens of houses and businesses, primarily belonging to Buddhist minorities, were set on fire or attacked. Buddhist temples became targets, and loudspeakers in local mosques were used to incite Bengali mobs, witnesses said.
In response, local authorities have imposed Section 144, a curfew-like measure, in Khagrachhari and Rangamati.
The interim government led by Nobel Peace Prize laureate Mohammad Yunus, which took power after deadly protests that led to the ousting of Prime Minister Sheikh Hasina last month, has expressed deep regret over the violence. It has told all security forces to exercise maximum restraint and prioritise the safety of all residents.
A high-level committee will be formed to investigate the violence, Home Affairs Adviser Lt Gen (Retd) Jahangir Alam Chowdhury said after a meeting with local political leaders and various organisations.
In the 1980s, the government resettled thousands of landless Bengali families in the 5,500 sq miles (14,200 sq km) CHT, fuelling tension between the new settlers and indigenous groups.
In 1997, the then government of Prime Minister Sheikh Hasina signed a peace accord with the Shanti Bahini, a tribal guerrilla group, ending a 25-year insurgency that sought political autonomy for the region.