President Evo Morales won a landslide victory in Bolivian elections yesterday bolstering his efforts to empower the country's indigenous majority under a socialist banner.

Exit polls and an unofficial count gave the country's first indigenous president an unassailable lead, prompting rival candidates to concede and supporters to celebrate in the capital La Paz.

"This process of change has prevailed," Morales told a cheering throng from the balcony of the presidential palace. He said the result, following a tumultuous first term that wrought sweeping changes over the Andean country, was a mandate for further transformation.

Opponents said the charismatic Aymara leader would become more radical and polarising and usher in an authoritarian personality cult.

Based on a count of 91% of votes, the polling firm Equipos-Mori gave Morales 63% of ballots, way ahead of a crowded field of nine candidates. His Movement Toward Socialism party won control of both chambers of congress, though in the lower house it was expected to fall just short of a two-thirds majority needed for constitutional changes.

Aymara and Quechua Indians queued from early morning to vote for the former llama herder who has nationalised key sectors of the economy, boosted social spending and clashed with the United States.

Bolivia's transformation was irreversible and redressed a historic injustice, said Fidel Surco, an indigenous leader and senate candidate for Morales' Movement Toward Socialism party.

"There is no way back, this is our time, the awakening of the indigenous people. We'll keep fighting till the end. Brother Evo Morales still has lots to do, one cannot think that four years are enough after 500 years of submission and oppression."

As well as pensions and subsidies to slums and impoverished rural highlands, the government has championed indigenous languages and traditional community justice, a "refounding" of the state cemented in a constitutional overhaul earlier this year.

"The decision is for change," Morales said after voting in the central coca-growing region of Chapare.

Inequality and poverty remain extreme, and land redistribution has been cautious, but indigenous voters backed Morales, 50, as an agent of transformation, said Mario Galindo, an analyst with the CEBEM thinktank.

The three political parties that ruled Bolivia for decades were all but wiped out. Within hours of polling stations closing, rival candidates had accepted defeat.

Manfred Reyes, a former army captain and state governor, came second with 27%, and Samuel Doria Medina, a cement magnate, came third with 6%, according to exit polls.

Reyes said the president would now have no restraint in following his ally, Venezuela's Hugo Chávez, down the road towards authoritarian ruin. "What's in play in this election is democracy," he said.

Doria Medina said the government's apparent economic success masked unsustainable populism. "The only sector that has had important growth is the coca sector and the cocaine industry."

Since 2005 GDP in Bolivia, one of South America's poorest countries, has jumped from $9bn to $19bn, pushing up per capita income to $1,671. Foreign currency reserves have soared thanks partly to revenue from the nationalised energy and mining sectors. The IMF expects the economy to grow 2.8% next year, stellar by regional standards.

But efforts to tap lithium deposits and increase gas production have faltered for lack of foreign investment. Relations with Washington are toxic: the US ambassador and US anti-narcotic officials were expelled as meddlers and spies.