Bangkok: Myanmar has barred a top United Nations investigator from visiting the country in what appears to part of a campaign to cover-up atrocities against Rohingya Muslims in Rakhine State.

Yanghee Lee, the UN's Special Rapporteur, lashed out at the government led by Nobel laureate Aung San Suu Kyi, saying she is "puzzled and disappointed by the decision" made only days before she due was to make an official visit.

"This declaration of non-cooperation with my mandate can only be viewed as a strong indication that there must be something terrible happening in Rakhine, as well as the rest of the country," Lee said in a statement released in Geneva.

Suu Kyi's government and Myanmar's military have rejected widely documented atrocities in Rakhine that the UN Human Rights Council has described as "very likely" crimes against humanity and human rights groups label genocide.