Navi Pillay, the U.N. commissioner for human rights, called for an investigation of the violence in Rakhine state in the western part of Myanmar, the U.N. News Center said.
"We have been receiving a stream of reports from independent sources alleging discriminatory and arbitrary responses by security forces, and even their instigation of and involvement in clashes," Pillay said in a news release.
She said at least 78 people have been killed and thousands of homes have been destroyed in the state.
Andrej Mahecic, a spokesman for the U.N. High Commissioner on Refugees, said many Muslims have said they are afraid to go back home.
In Iran, Supreme Leader Ayatollah Khamenei and other top officials Friday condemned anti-Muslim violence in Myanmar, Radio Free Europe reported. Two recent demonstrations, both sponsored by the government, have also been held in Iran to call on the international community to become involved.
RFE said the Iranian government has generally been silent about attacks on Muslims in countries it considers allies, including Russia and China.