Muslim residents of the multiethnic neighborhood where the attacks took place said Buddhist mobs had destroyed cars and attacked Muslim shops that were only a five-minute walk from a large police station. The police fired rubber bullets in an attempt to quell the violence, but residents complained that they had come too late.

“I don’t understand why it took the police 50 minutes to arrive,” said U Nyi Nyi, a Muslim resident who owns a tea shop in the neighborhood. “I don’t understand why police did not arrest members of the mob even though they were just a few feet away from them.”

Image A woman mourning her uncle, a 51-year-old man who was killed in fighting in Mandalay. Credit... Soe Zeya Tun/Reuters

Mr. Nyi Nyi said that he had witnessed the violence and that the crowds had shouted, “We are Buddhist martyrs!” and “Muslims, be gone!”

Religious violence, which has left more than 250 people dead and close to 150,000 homeless since rioting broke out in western Myanmar in June 2012, has been a major setback for Myanmar’s transition from a military dictatorship to democracy.

The government of President Thein Sein says it is trying to contain the violence and has blamed shadowy forces. Activists say the government is not doing enough and point to a set of laws proposed earlier this year by Mr. Thein Sein that they say reinforces the religious polarization. The laws would, among other things, require Buddhist women to obtain permission before marrying outside their religion.

A posting on Facebook by Ashin Wirathu, a Buddhist monk and spiritual leader of the radical Buddhist movement known as 969, appeared to have partly spurred the violence in Mandalay. He posted news of the reported rape and urged the government to crack down on what he called “jihadist Muslims.”