The ethnic fighting began overnight Saturday in Rakhine state near the border with Bangladesh, Voice of America reported.
Police and military troops implemented a curfew to stem the violence between the Buddhists and ethnic Rohingya, who are Muslims. Hundreds of buildings were set on fire, officials said.
Conflict between the two groups began June 3 when a group of Buddhists attacked a bus, killing 10 Rohingya because they believed they were responsible for the gang-rape and slaying of a Buddhist woman, Voice of America said.
Myanmar does not recognize the Rohingya as citizens, though about 800,000 live in the western region, the United Nations said.
U.S. State Department spokeswoman Victoria Nuland urged an immediate halt to the violence and encouraged the Myanmar government to investigate the incident in accordance with the rule of law.