"The Special Adviser calls for a full, impartial, and credible investigation of the disturbances to be conducted urgently as well as to ensure that the rule of law is enforced in a transparent manner," the United Nations said Friday in a news release.
State media said last week's outbreak of violence between ethnic Rakhine Buddhists and Rohingya Muslims resulted in 21 people killed, at least 20 wounded and at last 1,660 homes destroyed.
Nambiar was in the country formerly known as Burma the to participate in a meeting of the Peace Donor Support Group, as well as meet with government leaders in Naypyitaw, Myanmar's capital.
The violence prompted the government to declare a state of emergency.
U.N. Resident and Humanitarian Coordinator Ashok Nigam said more than 30,000 people have been displaced because of the violence.
Nambiar and Nigam traveled to the Rakhine town of Maungdaw with a government minister, where they visited camps housing the internally displaced persons and discussed the government's request for humanitarian assistance.
"The U.N. will work with the government and its humanitarian partners to meet these needs," Nigam's office said.