Myanmar has won international praise in the last two years for implementing sweeping political and economic reforms following a half-century of brutal military rule and isolation.
But the nominally civilian government of President Thein Sein has been largely silent as Buddhist mobs have gone on rampages in several cities, chasing down victims with metal pipes, chains and swords, and torching mosques and Muslim-owned shops and homes.
In addition to those killed, more than 140,000 people have been forced to flee their homes.
A police officer, who asked to remain anonymous because he was not authorized to speak to the media, said it was unclear who was behind Sunday's bombing.
A small device was placed under a car, he said, about 60 feet (18 meters) from where Wirathu was speaking.
Among the five injured was a young novice monk.
Wirathu immediately called it the "work of Islamic extremists."
"Ordinary Muslims wouldn't have done this," he told The Associated Press by telephone Monday from his monastery in Mandalay.
Wirathu, who once referred to himself as the "Burmese bin Laden," is the leader of 969, a fundamentalist movement that started on the fringes of society but now boasts supporters nationwide.
He has called for a boycott of all Muslim-owned shops and is pushing for a law that would restrict marriages between Buddhist women and Muslim men.
Soaring birthrates, he says, mean that Muslims, who today make up just 4 percent of the population, could one day become a majority.
Wirathu, who has come under heavy criticism in the international press, again lashed out again at Time magazine Sunday for a cover story earlier this month that plastered the words "Face of Buddhist Terrorism" under his photograph.
That too, he alleged, was the work of Muslim extremists, though he did not elaborate.
"The first threat to me was through the Time magazine," he said, and the second was Sunday, in the form of a bomb.
Thein Sein sought during a European tour, which wrapped up over the weekend, to clean up the image of a country gripped by sectarian violence, saying claims of "ethnic cleansing" in western Rakhine state were part of a "smear campaign" by outsiders.
The New York-based Human Rights Watch lashed back, saying that the president had "zero credibility," having done next to nothing to investigate atrocities, allegedly carried out with the backing of security forces.
The rights group pointed to several mass graves as evidence.
The president lifted a state of emergency Rakhine on Saturday several months ahead of schedule claiming peace and security had returned.
