Buddhist vigilantes in western Myanmar attacked a passenger bus and killed nine Muslims, police said on Monday, the deadliest communal violence in the tense region since a reformist government took power a year ago.

The bus was besieged near Taunggoke town in the western state of Rakhine on Sunday evening by a group who blamed some of its passengers for the murder of a Buddhist woman a week ago, said local residents and politicians. One of those killed was travelling in a separate car.

Rakhine is home to Myanmar's largest concentration of Muslims, but their presence is often resented by the Buddhist majority. The resentment is particularly sharp for Rohingya Muslims, whose roots date back to the 1820s when they were brought to the country as laborers by colonial power Britain.

Ko Kyaw Lay, a local Muslim and a human rights activist who belongs to an opposition party, said none of those killed were Rohingyas.

Police could not immediately confirm all of the details.

"An investigation is underway but I can't give you any further details," said a police official, who requested anonymity.

In a separate incident on Sunday in Sittwe, the Rakhine capital, 10 people were shot and wounded when riot police tried to break up a protest, witnesses said. They said the rally by some 200 people was unrelated to the attack on the bus.

Protesters threw rocks at police, who responded by firing into the air and a 13-year-old novice monk was among those wounded, the witnesses said.

Myanmar is one of Southeast Asia's most ethnically diverse countries, where sectarian and ethnic tensions still persist, despite a new political climate and broad reforms by a civilian-led government that says it has made peace and national unity a priority since it replaced a military junta 15 months ago.

In the case of the bus attack, Taunggoke resident Kyaw Min said the Buddhists "were angered by the authorities' handling" of an attack on a woman who locals say was raped by several men and then killed. Just before Sunday's attack, leaflets bearing a photo of the woman and describing the rape were distributed in the area.

Several residents, who asked for their names to not be disclosed, said the Muslims on the bus were not local and were on a visit to Rakhine state. They suggested those killed may not have been the perpetrators of the alleged gang rape and murder. REUTERS