The UN has called on Burma to investigate reports that scores of Rohingya Muslims have been killed in attacks by Buddhists in Rakhine state.
UN human rights chief, Navi Pillay said a “full, prompt and impartial investigation” was needed.
The UN had “credible information” that 48 Rohingya Muslims had been killed in violence in early January.
The Burmese government has rejected the claims as groundless.
Presidential spokesman Ye Htut said the UN was not listening to its own staff on ground and was damaging its reputation in Rakhine state.
The western state of Rakhine, which is also known as Myanmar has witnessed several outbreaks of violence targeting the Rohingya Muslims since June 2012.
In the statement, the UN said eight Rohingya Muslim men were attacked at Du Char Yar Tan village on 9 January.
On 13 January, a police official was killed in the same village by Rohingya Muslims.
In retaliation, at least 40 Rohingya men, women and children by local security forces and Rakhine people, the UN statement added.
The government statement only acknowledged the death of the police sergeant.
Ms Pillay said: “I deplore the loss of life … and call on the authorities to carry out a full, prompt and impartial investigation and ensure that victims and their families receive justice.
“By responding to these incidents quickly and decisively, the government has an opportunity to show transparency and accountability, which will strengthen democracy and the rule of law in Myanmar.”
The Rohingya Muslims people are considered stateless and are rejected by both Burma and neighbouring Bangladesh.
At least 200 people, mainly Muslim women and children were killed by Buddhists in Rakhine state in 2012.
Thousands of Rohingya Muslims remain displaced in the wake of that violence, many still living in refugee camps.
Spontaneous outbursts of anti-Muslim violence have become quite frequent and have continued throughout 2013 in other parts of Burma.
Last week, more than 30 Rohingya Muslims were murdered in attacks by Buddhists in Rakhine state.
A mass killing had taken place in a joint attack by local Buddhists and security forces.