The UN rights body has decided to "urgently dispatch" an independent fact-finding mission to Myanmar.
The UN rights council agreed on Friday to "urgently" launch an investigation into violations against Rohingya Muslims, including torture, murder and rapes allegedly committed by Myanmar's security forces.
A UN report issued last month, based on interviews with 220 Rohingyas among 75,000 who have fled to Bangladesh since October, accused Myanmar's security of human rights violations against Rohingyas in northern Rahkine state.
The UN Human Rights Council decided to "dispatch urgently an independent international fact-finding mission" to Myanmar, in a resolution adopted by consensus.
But Myanmar ambassador Htin Lynn, speaking before the decision rejected the move as "not acceptable." Myanmar's national commission had just interviewed alleged victims who fled to Bangladesh and would issue its findings by August, he said.
The Geneva-based body adopted the resolution without a vote, brought by the European Union and supported by countries, including the United States, that called for "ensuring full accountability for perpetrators and justice for victims."
China and India said they would "disassociate" themselves from the consensus, with China's delegation saying the issue "cannot be solved overnight."
Myanmar has long faced international condemnation for its treatment of the Rohingya, who many in the Buddhist majority reject as illegal immigrants from Bangladesh.
The issue has reached boiling point in recent months after the army launched a bloody crackdown in the north of Rakhine following deadly attacks on several police border posts in October.