The killings were part of a larger army crackdown on the Rohingya, beset by allegations of murder, rape, arson and looting, unleashed in response to Rohingya militant attacks on security forces in late August.
The foreign ministers Asia-Europe Meeting, or ASEM, opening in the Myanmar capital Naypyitaw is an important multilateral diplomatic gathering which happens once every two years and is designed to discuss issues between Asia and Europe.
"The widespread threat and use of sexual violence was clearly a driver and push factor for forced displacement on a massive scale and a calculated tool of terror aimed at the extermination and the removal of the Rohingya as a group," the UN said.
Some 600,000 of the stateless minority have fled to Bangladesh since late August carrying accounts of murder, rape and arson at the hands of the Myanmar's army, after militant raids sparked a ferocious military crackdown.
Since the crisis began media and international NGOs have only been given highly controlled access on officially-steered visits. Myanmar denies the Rohingya citizenship, describing them as "Bengali" interlopers.
Thailand does not recognise the status of any refugees or recognise the Rohingya as legitimate migrant workers. Thailand said it supported a statement on the issue by the Association of Southeast Asian Nations (ASEAN), a grouping of 10 nations.
About 422,000 refugees from Myanmar have poured into Bangladesh since August 25, 2017. Attacks by Rohingya militants on security posts triggered an offensive response by Myanmar army that has led to this humanitarian crisis. Indian Express’ Praveen Swami reports on the emerging security nightmare from the Myanmar-Bangladesh border.