Extra troops have been sent to the troubled western state of Rakhine, the government said Saturday.
The deployment of an additional army battalion -- around 500 soldiers -- led the UN to call for restraint in the region, which earlier this year saw a massive security operation that led to widespread human rights abuses.
In a statement issued to state-run media, State Counselor Aung San Suu Kyi's office said the extra forces had been sent to the Maungdaw area of northern Rakhine, where curfews were introduced earlier this week.
The government said 59 civilians had been killed and 33 had gone missing in the area up to Wednesday.
"The government will resolutely take effective action against these terrorist acts in accordance with law," the statement said.
"Actions will be taken against all extremists and those who abet their extremism."
Last October, a security crackdown was launched after nine police officers were killed in Maungdaw.
In a report on the four-month operation, the UN said it had uncovered human rights violations by security forces in Rakhine that indicated crimes against humanity.
During interviews with Rohingya Muslim refugees in neighboring Bangladesh, the UN documented mass gang rape, killings, including of babies and children, brutal beatings and disappearances.
Last month, the government refused entry to a UN team probing the allegations.
Representatives of the Rohingya minority have said approximately 400 people were slain during the operation.
In a statement on Thursday's troop deployment, the Office of the UN High Commissioner for Human Rights said: "This development… is a cause for major concern. The government must ensure that security forces exercise restraint in all circumstances and respect human rights in addressing the security situation in Rakhine state."
Thousands of Rohingya have sheltered in refugee camps in Rakhine since communal violence flared in mid-2012.
The state is home to around 1.2 million Rohingya, who have long been officially labelled "Bengali" -- a term suggesting they are illegal immigrants from Bangladesh.
Despite having lived in the area for generations, Rohingya have been effectively denied citizenship by a 1982 nationality law and have restricted basic rights such as freedom of movement.
