Myanmar President Thein Sein blamed "political opportunists and religious extremists" for violence between Buddhists and the Muslim minority in the country. The violence has claimed at least 40 lives since March 20.
Thein Sein was quoted by regional newspaper The Irrawaddy as saying he would use force "as a last resort" to quell the violence.
U.N. special envoy on human rights Tomas Ojea Quintana said Myanmar needs to take swift action to keep the conflict from spreading and undermining reforms.
"Tackling discrimination is fundamental to establishing the rule of law and impunity for acts of violence and discrimination must no longer be tolerated," Quintana said in a statement.
Myanmar earned praise for political reforms that began with general elections in 2010. Human rights groups say the latest outbreak of violence is jeopardizing those efforts, however.
Quintana said discrimination against the Muslim minority was fueling tensions from similar conflicts last year in Rakhine, which left nearly 200 people dead.
Myanmar imposed a state of emergency over parts of the Mandalay region last week in response to the conflict. The United Nations estimates at least 12,000 are displaced by violence.