Tension is growing high in Bolivia as the energy-rich Tarija area voted overwhelmingly to seek greater autonomy from the central government.

The referendum in Tarija, the smallest of Bolivia's nine provinces but home to more than 80 percent of its vast natural gas reserves, followed similar ballots in the Amazon regions of Pando and Beni, and wealthy Santa Cruz.

Evo Morales, the country's first indigenous president has called the votes 'illegal and separatist'. His supporters called for a boycott, and more than a third of Tarija's 173,000 registered voters did not cast ballots, early results showed.

Partial results carried by local television showed 80.3 percent of voters backed the autonomy plan, which would, in theory, give local leaders control over taxes, policing and natural resources, Reuters reported.

"We need to give ourselves an opportunity, and autonomy will give us the deep-rooted change we need, a real change that will unite Bolivia," Tarija Governor Mario Cossio said.

Previous referendums, organized by rightist local governors, saw violent clashes between pro- and anti-Morales demonstrators but election officials in Tarija said Sunday's voting was generally calm.

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