Bolivians are voting in a presidential election following last year’s turmoil which ended the 13-year rule of left-wing President Evo Morales.
Mr Morales resigned and fled the country, having declared victory in a disputed vote subsequently annulled.
His Movement Towards Socialism (Mas) party candidate, Luis Arce, has been the consistent favourite to win.
The main challenger is former President Carlos Mesa, the centrist candidate of the Citizens’ Community alliance.
If neither of them succeeds in obtaining more than 50% of the votes or 40% with a 10-point lead over the nearest challenger, a run-off will be held on 29 November.
Sunday’s vote is on a new president, vice president and 166 members of congress.
The race has already been postponed twice due to coronavirus concerns, and political tensions are high
Who are the candidates?
Before running for president, Mr Arce served as economy minister under former President Morales.
As minister, he oversaw the nationalisation of Bolivia’s mining, gas and telecommunications industries. Mr Arce also helped to launch the Bank of the South, of a regional development fund for infrastructure and social development projects.
23years since he got am MSc in economics from Warwick Uni
11years he served as finance minister under Evo Morales
2months he spent abroad following Evo Morales’s resignation
Source: BBC Monitoring
Mr Mesa, his major rival, was president of Bolivia between 2003 and 2005. His rule was marred by internal tensions about ownership of the country’s vast gas resources.
Before his career in politics, Mr Mesa worked as a journalist and set up a television news production company, PAT, which he transformed into a national network.
14months he served as vice-president between 2002 and 2003
19months he served as president after his predecessor resigned
21number of books he has authored or co-authored
Source: BBC Monitoring
Why are tensions so high?
Days after Mr Morales announced his resignation last year, conservative Senator Jeanine Áñez took over as interim president.
She said her task would be to lead the country to an election re-run. But electoral authorities postponed the race until 3 May, then to 6 September and finally to 18 October as Bolivia grappled with a large coronavirus outbreak.
Mr Arce’s Mas party and other critics have accused the government of using the pandemic to try to hold on to power.
In September, Ms Áñez announced that she was bowing out of the presidential election, saying she did not want to split the vote and see Mas return to power.
Animosity has been building for months, and the United Nations has registered 46 incidents of violence during the election race. Several international groups, including the UN and Catholic Church, have called on all sides to avoid confrontation.
The interim government has alleged that Mas and allied groups are preparing violent acts if Mr Arce does not win, and said the armed forces were “ready” for any eventuality.
Tensions have also flared after a last minute announcement by Bolivia’s electoral body, which said it would not release fast-count results on Sunday night, citing system issues.
Mr Acre has said the decision could “generate doubts” about the vote count’s legitimacy.
What about Evo Morales?
This will be the first presidential election since 2002 in which Mr Morales is not on the ballot. Violence and protests erupted in the country last year after he won an unconstitutional fourth term of office.
Evo Morales, 60, has been leading the Mas party’s campaign from exile in Argentina, supporting Mr Arce, and making his voice and opinions heard through media interviews and social media. He has portrayed the Áñez government as a right-wing “dictatorship”.
The former leader of the coca growers’ union still commands considerable support in Bolivia among its indigenous population and unions.
Mr Morales said in late September that, if Mr Arce won, he would return to the country “the next day”.
On Sunday, he appealed for the elect