Colombians are heading to polls to vote for a president in the tightest election in decades that has the power to determine whether the country continues peace talks with leftist guerrillas to end its 50-year conflict.

Sunday’s vote has become a referendum on President Juan Manuel Santos' strategy of negotiating disarmament of Revolutionary Armed Forces of Colombia (FARC) rebels to end bloodshed that has killed more than 215,000 people left 5.7 million internally displaced since 1968.

President Juan Manuel Santos, who is seeking a second four-year term, has presented his re-election as a referendum on his negotiations to end the  conflict with the Marxist fighters.

Santos appeals to Colombians who hope the guerrillas will finally lay down arms after seeing top leaders killed and their numbers halved to about 8,000 fighters.

"Peace is the hope for humanity, and Santos is peaceful, not a warrior," said Arley Bustos, 48, who was selling umbrellas and World Cup stickers on a street Bogota. "Peace will bring us progress."

All politicians promise peace, but we haven't seen progress and the guerrillas keep killing soldiers.

Otilia Tibovizco, Colombian citizen

However, his main rival, right-wing candidate Oscar Zuluaga, has vowed to take a harder line and freeze  the 18-month-old negotiations until the guerrillas stop their "criminal actions  against Colombians."

Santos and Zuluaga hav been polling neck-and-neck following a race marred by accusations of electronic espionage and drug-linked campaign financing.

Currently, neither candidate is seen winning enough votes to avoid a June 15 run-off.

FARC political gains 

Meanwhile, talks in Cuba between FARC members and the Colombian government have yeilded few agreements. 

With particular agreements made on agriculture and political participation for FARC, other issues remain including serving jail time and details of demobilisation.  

While Colombians are desperate to see an end to the violence, many are outraged that guerrilla leaders accused of crimes against humanity could possibly be pardoned or hold political office.

"All politicians promise peace, but we haven't seen progress and the guerrillas keep killing soldiers," said Otilia Tibovizco, 60, selling food on a Bogota street corner.

Zuluaga has traveled the country with Uribe, from coca farms in the south to cattle ranches in the northwest, reminding voters of how Uribe's confrontation of insurgents gave Colombia its biggest security gains since war broke out in 1964.

Polls show him surging over the last month to catch or even overtake Santos.

Those surveys may not reflect last-minute scandals including accusations that Zuluaga's campaign sought to sabotage the peace talks by hacking the negotiators' emails and allegations that Santos took drug money during his 2010 campaign.

Both deny wrongdoing.