Colombians re-elected President Juan Manuel Santos on Sunday in a cliffhanger seen as a referendum on peace talks with FARC guerrillas.
The center-right Santos registered 50.95 percent of the vote, compared with 45 percent for the more conservative Oscar Ivan Zuluaga, according to the electoral board. Another 4.03 percent were blank protest votes.
Santos, 62, who governs in a coalition with some leftist parties, has led efforts to reach a peace deal the leftist Revolutionary Armed Forces of Colombia. In contrast, Zuluaga called for stricter conditions as a pre-requisite to any deal.
"The message sent today is also for the FARC and ELN," Santos said as cheering supporters at his headquarters chanted "Colombia wants peace!"
"This is the end. And we have to get there by standing firm. This is the end of more than 50 years of violence," said Santos, whose government also has reached out to the smaller leftist National Liberation Army (ELN) rebels seeking peace.
Seeking to shoot down his rival's main slogan, Santos added: "This is not going to be peace with impunity. It will be a fair peace. We have to take the steps to ensure that it is not only fair, but lasting."
The bid to end Latin America's longest guerrilla war was the central issue of the run-off, which descended into mudslinging between the two candidates.
Zuluaga, 55, long opposed the peace talks and campaigned under the slogan "No to impunity." But he now has said that he would negotiate with the rebels under stricter conditions.
Santos, however, drew more support arguing that Colombians had to choose between "the end of the conflict, or an endless conflict."
After Santos won, Zuluaga offered his congratulations, saying "this is what democracy is about."
The conflict, with its violent cocktail of rebels, paramilitary militia and criminal gangs, has left more than 220,000 people dead and forced five million to leave their homes over the past half century.
University of the Andes political analyst Felipe Botero said that in a tight race, "Santos got a boost from many voters who cast ballots for him because they want the peace process to continue, not necessarily because they support what his government has done" broadly.
Words of congratulations poured in from across the region, including from the United States and neighboring Venezuela.
"We look forward to continuing to work with President Santos and his administration to advance our bilateral relationship and to continuing to support the Colombian Government and people as they pursue a negotiated end to the conflict there," US Secretary of State John Kerry said in a statement.
Venezuelan President Nicolas Maduro, unofficial leader of the hard left across the region, said "a debate was opened on whether peace should be sought, or not, and the Colombian people have clearly voted on a road to peace."
Though the economy is growing more than four percent a year, A third of Colombia's 47 million residents live in poverty.
"Social issues are more visible but they remain linked to peace, which the president has kept as the central pillar of his campaign," said political scientist Patricia Munoz Yi from Javeriana University in Bogota.
The peace process, recently expanded to also include the smaller ELN guerrilla group, would have collapsed with a Zuluaga victory, said Vicente Torrijos, a political scientist at the Universidad del Rosario.
Founded in the 1960s, the ELN and the FARC are the last leftist guerrilla armies operating in Colombia. They boast 2,500 and 8,000 fighters respectively.
Talks in Havana with the FARC that began in November 2012 have resulted in agreements on three topics of a six-point agenda.
But at least three major issues remain unresolved: the surrender of weapons, compensation for victims and how a final agreement would be ratified.
Zuluaga's conditions for talks with the FARC included a permanent guerrilla ceasefire and jail time for its leaders.