Ever since Indonesia achieved independence in 1949, the Jakarta government has faced a constant battle to keep the nation's 13,000 islands together.
Click on the map below for some of the main areas of conflict.
Kalimantan - the Indonesian part of the island of Borneo - has suffered from a number of outbreaks of inter-ethnic violence in recent years.
In the late 1990s, long-running tensions between the indigenous Dayak people and migrants from the island of Madura finally spilled over in a series of violent attacks.
In 2001, hundreds of people were killed and tens of thousands of Madurese were forced to flee the island, pursued by enraged Dayaks.
Thousands of Madurese left Kalimantan after the 2001 clashes
Tensions between the two communities had been rising for decades, in the wake of an influx of Madurese under the central government's transmigration programme.
Transmigration started at the beginning of 20th Century, but it was not until President Suharto came to power in 1966 that large numbers of people began to arrive in Kalimantan from other parts of Indonesia.
By 2000, transmigrants made up 21% of the population in Central Kalimantan, and the demographics of the region had changed dramatically.
The Dayaks resented the increased competition for land and jobs, and many felt the newcomers were unfairly favoured at the expense of the indigenous community.
New laws gave the government power to reallocate land for commercial logging, mining and the construction of plantations for palm-oil and paper production.
Migrants - especially the Madurese - assumed control of much of these industries.
KALIMANTAN: KEY FACTS
Makes up two-thirds of the island of Borneo
The rest of Borneo is part of Malaysia
Non-Muslim Dayaks form the majority of the population
Muslim Madurese arrived in the 1950s and 60s
The Madurese were not the largest migrant group in Kalimantan, but they were the principal target of Dayak anger because of their greater wealth and the long-held stereotypes each group held about the other.
Under President Suharto's regime, the military suppressed any attempts at violence between the two groups.
But after his fall from power in 1998, the central government intervened much less in local matters, encouraging the Dayaks to take matters into their own hands.
Violence erupted in West Kalimantan in 1996-1997, and again in 1999.
But the worst incidents happened in February 2001, when at least 500 Madurese were killed in the Central Kalimantan timber town of Sampit.
Some of the dead bodies were decapitated in a ritual reminiscent of the Dayak's head-hunting past.
More than 100,000 Madurese were forced to flee the area to escape the massacre.
The violence spread out into other areas of the province, and by April 2001 almost the entire Madurese community had left Central Kalimantan.