Bolivians have voted amid deep divisions between the supporters of former president Evo Morales' leftist MAS party and its opponents, with no major incidents initially reported despite concern over possible violence.
Long queues were reported at many polling stations on Sunday , with more than 7 million people eligible to elect a president and a congress in the rerun of elections held a year ago that were later voided.
In that poll, Morales claimed to have won a fourth term but fraud allegations, violent protests and pressure from the military forced the Andean country's first indigenous president to go into exile.
Right-wing senator Jeanine Anez then took power as interim president.
The presidential candidate of Morales' Movement for Socialism, Luis Arce, is now seen as a good chance of defeating centrist Carlos Mesa, who was hoping to attract Anez supporters after she withdrew from the race.
But if Morales' former economy minister does not secure more than 50 per cent of the vote or 40 per cent with a 10-point advantage over Mesa, the election will go to a run-off which the MAS could lose if the conservative camp unites behind the centrist ex-president.
Dozens of violent incidents in the run-up to the poll had sparked concern that Bolivia could see a repeat of last year's fraud claims and clashes involving Morales' supporters, opponents and police, which left more than 30 people dead.
A heavy military presence was reported outside some polling stations on Sunday.
Mesa urged calm and patience after casting his ballot, while Arce said he hoped election day and the following days would "pass in a peaceful manner".
Salvador Romero, the president of the Supreme Electoral Tribunal (TSE), said the vote was proceeding in "peace, tranquillity, calm".
MAS supporters say Morales presided over unprecedented stability and growth during his 13 years in power, with poverty going down by 40 per cent.
They see the main anti-MAS parties as representing a racist white or mestizo elite indifferent to the interests of the country's large indigenous population.
Anez's government has meanwhile been accused of handling the coronavirus pandemic - which has claimed more than 8400 lives - badly as well as of corruption and repressing the opposition.
Australian Associated Press