The UN has called on Myanmar to investigate new reports of human rights violations, including the killing of unarmed people and torching of rural settlements in the Muslim-majority Rakhine state.
Myanmar deployed troops to Rakhine earlier this month following alleged attacks on police posts along the border with Bangladesh, which authorities blamed on Rohingya Muslims.
Officials say security forces have slain 30 attackers and arrested 53 suspects while hunting for at least 400 other suspected militants.
The identity of those militants has not been revealed yet because Rohingyas have no known militant group.
UN Special Rapporteur on the human rights situation in Myanmar Yanghee Lee said state authorities had promised to launch proper investigation into the incident and not accuse anyone until “solid evidence” was obtained.
“Instead, we receive repeated allegations of arbitrary arrests as well as extrajudicial killings occurring within the context of the security operations conducted by the authorities in search of the alleged attackers,” she said on Monday.
Rights groups say troops have gone on a rampage, which has forced terrified civilians to flee their homes. Reports of summary executions of civilians, including of children, during searches and raids have abounded.
“Reports of homes and mosques being burnt down and persons of a certain profile being rounded up and shot are alarming and unacceptable,” said UN Special Rapporteur Agnes Callamard said.
“The authorities cannot justify simply shooting suspects down on the basis of the seriousness of the crime alone," she said.
"The authorities have the duty to take concrete measures to prevent extrajudicial killings in the country, not to perpetuate them,” she added.
The UN Office for the Coordination of Humanitarian Affairs (UNOCHA) said up to 15,000 mostly Rohingya Muslims have been displaced from their villages in Rakhine in the wake of the recent military raid.
Rakhine, home to around one Rohingya Muslims, has been the scene of communal violence at the hands of Buddhist extremists since 2012.
Hundreds of people have been killed, while tens of thousands have been forced to flee their homes and live in squalid camps in dire situations in Myanmar and other countries in Thailand, Malaysia and Indonesia.
According to the UN, Rohingyas are one of the most persecuted minorities in the world.
The government denies full citizenship to Rohingya population, branding them illegal immigrants from Bangladesh, even as many trace their lineage in Myanmar back generations.