Widespread violence in the city of Meiktila broke out March 20-23 following a fight between a Buddhist shopper and a Muslim store owner. Human Rights Watch analyzed satellite images and said more than 800 buildings were destroyed, almost all in Muslim enclaves.
Myanmar, former called Burma, has a history of violence against Muslims, said Brad Adams, Human Rights Watch Asia director.
"The government should investigate responsibility for the violence in Meiktila and the failure of the police to stop wanton killings and the burning of entire neighborhoods," Adams said. "Burma's government should have learned the lessons of recent sectarian clashes ... and moved quickly to bolster the capacity of the police to contain violence and protect lives and property."
Myanmar has been credited recently with political reforms dating back to 2010, but rights advocates say the outbreak of violence jeopardizes the reforms.
A U.N. special envoy said last week prejudice and discrimination may be inciting religious violence in central Myanmar, but Myanmar President Thein Sein blamed "political opportunists and religious extremists" for the violence.