Hundreds of houses are reported to have been burned down in villages around the town of Sambas, in the province of West Kalimantan, and thousands of people have been forced to seek refuge.

Using a shoot-to-kill order, police and soldiers forced hundreds of rioters armed with knives and swords to return to their homes, leaving bodies in the streets.

The BBC's Jonathan Head: "An unstoppable outburst of community anger"

The unrest has involved indigenous Dayak and Malay communities fighting immigrants who had resettled in the area from the island of Madura, off eastern Java.

Two years ago several hundred Madurese immigrants were killed by Dayaks trying to drive them out of West Kalimantan.

The latest trouble reportedly broke out after a Madurese man was discovered carrying a concealed weapon, in defiance of an agreement between the ethnic communities.

Jakarta Correspondent Jonathan Head looks at the grievances behind the unrest

There has been widespread sectarian violence in many areas of Indonesia in the past year. More than 200 people have been killed in clashes between Christians and Muslims on the eastern island of Ambon since January.

Ethnic, not religious hatred

BBC Jakarta Correspondent Jonathan Head says it appears that the latest Borneo conflict is an ethnic, not religious dispute.

Hundreds were killed in recent riots in Ambon

Local Malays have joined the indigenous Dayaks in attacking the Madurese. Both the Malays and the Madurese are Muslim, whereas the Dayaks tend to be Animist or Christian.

The Dayaks, who used to live a semi-nomadic existence in the forest, now find themselves marginalised in a plantation and timber-based local economy in which outsiders often have the best jobs.

Immigrants from Madura have long been accused by the Dayaks of aggression and insensitivity to Dayak customs.

Two years ago thousands of Dayak men attacked Madurese villages, burnt them down and dismembered their inhabitants.

Now local people report that at least one severed head was displayed during the clashes of the past two days.

Our correspondent says that as in Ambon, the conflict in western Borneo pits local communities against recent immigrants - a legacy of a government policy of encouraging people from the overcrowded parts of the country to move to the outer islands