The left-wing Evo Morales is known as the "peasant president"
President Evo Morales has claimed victory in Bolivia's presidential election and appears set to serve a second five-year term.
Exit polls suggest Bolivia's first indigenous leader polled at least 61%, defeating his conservative rivals.
Mr Morales, who had vowed to expand state control over the economy, said it was now his duty to "accelerate the pace of change".
A referendum earlier backed changes to allow presidents to seek a second term.
Mr Morales, 50, won between 61% and 63% of the vote, avoiding a run-off, the exit polls suggest.
Emilio San Pedro, BBC News
With this apparent victory, Evo Morales doesn't only gain a second term in office. He's also now freed of any real opposition in Congress, where his Movement to Socialism party is expected to win an outright majority in both the lower house and the Senate.
This newfound political freedom will give Mr Morales the opportunity to push through his sweeping social reforms - which he says are aimed at improving the lives of the more than 30% of Bolivians who live on less than $2 a day.
But despite what appears to be a landslide victory, Mr Morales is still likely to continue facing stiff opposition to his socialist agenda from the country's wealthy, eastern provinces like Santa Cruz. There, the main opposition candidate, Manfred Reyes Villa, appears to have won the majority of the votes.
They indicate that his main rival Manfred Reyes Villa, a former governor, secured about 23%.
The BBC's Andres Schipani in La Paz says the exit polls also suggest the president is set to take control of the upper house of Congress from the opposition.
Mr Morales said that "by holding two-thirds of Congress it now is my duty to accelerate the pace of change".
Official results are expected in the coming days.
Foreign observers have praised the election for its transparency and fairness.
Mr Morales's support base is chiefly among poor indigenous people who account for some 65% of the population - in contrast to his challengers.
"He's changing things. He's helping the poor and building highways and schools," Veronica Canizaya, a 49-year-old housewife, told Reuters news agency before casting her vote at a public school on the shores of Lake Titicaca.
Analysts say a victory for Mr Morales will solidify his dominance in Bolivian politics and weaken the split conservative opposition tied to the business elite.
His other challenger was Samuel Doria Medina, a wealthy businessman.
Both challengers accused Mr Morales of having "totalitarian" ambitions for the country and of being responsible for the rise in cocaine production, says our correspondent, Andres Schipani.
Mr Morales told crowds at his final campaign rally: "There are two roads: continue with change or return to the past."