The United Nations applauded the maintenance of a ceasefire in Colombia despite the vote and said its special envoy, Jean Arnault, would also travel to Cuba to help the process.
"We would have hoped for a different result, but I am encouraged by the commitment expressed (by Santos and Timochenko)," U.N. chief Ban Ki-moon said. "I count on them to press ahead until they achieve secure and lasting peace.
Colombians, even those who backed the "No" vote, expressed shock at the outcome and uncertainty about the future.
"We never thought this could happen," said sociologist and "No" voter Mabel Castano, 37. "Now I just hope the government, the opposition and the FARC come up with something intelligent that includes us all."
The peace accord reached in late August and signed a week ago offered the possibility that rebel fighters would hand in their weapons to the United Nations, confess their crimes and form a political party rooted in their Marxist ideology.
It was supposed to be the day when Colombians closed the book on 52 years of armed conflict. Instead, voters defied opinion polls and their president Sunday by rejecting — albeit by the slimmest of margins — a historic peace treaty that's been years in the making.
The ballots were almost evenly split with the No vote topping the Yes vote by a mere 0.5 per cent. The margin of victory was about 54,000 votes among the 12.7 million ballots cast in a plebiscite that asked voters whether or not they supported an agreement to end the war between government troops and the Marxist guerrilla group known as the FARC.
The result, a kind of Colombian "Brexit" shocked the political system and threw a four-year-old peace process into chaos. It's now unclear whether a bilateral ceasefire will hold, whether the FARC will follow through on plans to disarm, and whether a UN mission tasked with verifying compliance with the peace accords will be sent home.
"It's really a leap into the unknown," said Adam Isacson, a Colombia expert at the Washington Office on Latin America.
The reason the deal narrowly failed was that the voters felt the rebels, who had killed many Colombians, were getting off scot-free. They wanted some sort of punishment.
Polls have just closed in Colombia's national referendum on a peace deal with leftist rebels. Now the wait for results begins.
A few governors and lawmakers had been hoping to extend Sunday's voting by two hours to accommodate those who stayed home amid heavy rainfall caused by Hurricane Matthew along Colombia's Caribbean coast. But electoral authorities rejected the proposal.
Authorities say early results should be available within an hour of polls closing.
Heavy rains resulting from Hurricane Matthew are delaying the opening of some polling stations in rural parts of Colombia as the country votes on whether to ratify a peace deal between the government and rebels.
The Interior Ministry says 82 voting booths in La Guajira peninsula, the area hardest hit by Matthew, didn't open as scheduled due to logistical problems triggered by flooding and bad weather.
Columbia and Colombia are easily confused. Add in the fact that Columbus is actually Colombo,