Peruvians headed to the polls Sunday in a presidential election run-off between a leftist ex-army colonel and the daughter of jailed former strongman Alberto Fujimori.
Opinion polls have given former military man Ollanta Humala, 48, a slight lead over Keiko Fujimori, a 36-year-old right-wing lawmaker whose father is serving a lengthy jail sentence for human rights abuses and corruption.
"It will be a close race that is likely to have a photo finish," predicted Fernando Tuesta, director of the Institute for the Study of Public Opinion at Lima's Catholic University.
The last two opinion polls, from Datum and Ipsos-Apoyo, showed a lead of between 1.6 and 3.8 percentage points for Humala over Fujimori.
Faced with the two most extreme candidates to emerge from April's first round poll, many voters said they would choose the person they disliked the least.
Polling stations for almost 20 million eligible voters were to open at 8:00 am (1300 GMT) and close at 4:00 pm (2100 GMT).
Amid escalating tensions, the military announced late Saturday that three soldiers deployed to provide security for the election had been killed in a clash with leftist guerrillas from the Shining Path group.
Six other soldiers were wounded when the army patrol was ambushed in the valley of the Rivers Ene and Apurimac, in the southeastern province of La Convencion, where the soldiers were to provide security at polling stations.
Both Fujimori and Humala drew support with promises to help around one third of the population of some 29 million still living in poverty despite a decade of record growth on the back of mineral exports.
Security and corruption were also key issues as the campaign polarized in the second round.
Fujimori campaigned in the shadow of her notorious father who is serving a 25-year jail sentence for corruption and rights abuses during a clampdown on the Shining Path during his 1990-2000 rule. He is also remembered for reining in hyperinflation.
Surrounded by many of his allies, she failed to convince detractors that she would not follow in his footsteps and possibly seek to release him from jail, after serving as the country's First Lady at the age of 19 following her parents' separation.
But she wooed investors, most of the media and conservative ex-presidential candidates with promises of sticking to the model of free-market economics which has accompanied an unprecedented decade of growth.
Humala, who is of Indian origin like 80 percent of Peruvians, promised a fairer distribution of the country's riches, particularly in southern Andean provinces where poverty reaches 60 percent. His rise sent shockwaves through Lima's stock exchange.
Humala first came to prominence in 2000 when he led a short-lived military rebellion against Fujimori's father, and he has also been accused of rights abuses which have never been proved.
Both candidates sought to remove doubts over their credibility as they increased attacks on each other in the run-up to the vote to replace President Alan Garcia.
Fujimori used former New York City mayor Rudolph Giuliani to help reassure on security and Peruvian ex-prime minister and ex-World Bank economist Pedro Pablo Kuczynski to help boost her credentials.
Humala garnered support from artists and intellectuals angered by the prospect of a return of the Fujimori dynasty, such as Nobel Prize-winning author Mario Vargos Llosa, a former presidential candidate who lost to Fujimori in 1990.
But many voters in Peru, where voting is mandatory, were not excited about either of the candidates.
"I don't know who I'll vote for, but I know it will be a vote against one of them," said Maria Hidalgo, a 45-year-old teacher in Lima, on the eve of the election.