The Colombian government and FARC rebels scrambled Monday to save a peace deal after voters narrowly rejected it in a referendum, throwing the four-year-old peace process into uncertainty.

President Juan Manuel Santos, who has staked his legacy on ending the 52-year-old conflict, called an emergency meeting with leaders of the country's political parties to try to chart a way forward after the shock referendum defeat Sunday.

A visibly crestfallen Santos said as he arrived that the meeting would seek "common ground and unity."

"That's more important now than ever," he said.

The leader of the Revolutionary Armed Forces of Colombia (FARC), Rodrigo Londono, meanwhile said in a video from Havana -- where the peace talks were held -- that the Marxist guerrillas, like the government, remained committed to an ongoing ceasefire.

Londono -- better known by the nom de guerre Timoleon "Timochenko" Jimenez -- said the rebels were prepared to "fix" the rejected deal.

The result "does not mean the battle for peace is lost," he said.

UN Secretary General Ban Ki-moon, who had offered a UN team to oversee the disarmament process, said he had "urgently" sent his Colombia envoy to Havana for new consultations.

But the outcome left no clear path to end a conflict that has claimed more than 260,000 lives and left 45,000 missing.

Opinion polls had showed the "Yes" camp well ahead, and negotiators had said there was no Plan B in the event of a "No" vote.

The peace deal had been hailed as historic from the time it was concluded on August 24 to the moment it was signed last week in the presence of UN chief Ban and US Secretary of State John Kerry.

But resentful of the blood shed by the Marxist guerrillas and the lenient punishment the deal meted out for their crimes, voters rejected it by a razor-thin margin: 50.21 percent for the "No" camp to 49.78 percent for "Yes."

Voter turnout was low, at just over 37 percent.

- New talks? -

A referendum was not required to adopt the deal, but Santos insisted on holding one to ensure its legitimacy.

The head of the government's delegation to the peace talks, Humberto de la Calle, offered his resignation, saying he did not want to be "an obstacle to what comes next."

That could pave the way for fresh negotiations, with a new government team including hardliners allied with Santos's top political rival, former president Alvaro Uribe, who led the "No" campaign.

But Uribe's right-wing party, the Democratic Center, was notably absent from the meeting Santos held Monday at the presidential palace to assess the options for the future of the peace process.

- Hatred of the FARC -

Commentators compared the result to that of June's surprise "Brexit" vote for Britain to leave the European Union.

Forecasts apparently miscalculated Colombians' desire to punish the FARC.

Deal opponents resented concessions that included soft sentences with no jail time for rebels who confessed to their crimes.

The accord called for the 5,765 FARC rebels to disarm and become a political party, with seats in Colombia's Congress.

That did not sit well with some Colombians who remember the FARC for massacring civilians, seizing hostages and sowing terror in a multi-sided conflict that has seen atrocities committed all around.

"How should we respond to the damage they've done to the nation? That sums it all up," said political analyst Jorge Restrepo, head of the Conflict Analysis Resource Center (Cerac) in Bogota.

- Nobel hopes dashed -

Santos and Londono had been tipped as top contenders for this year's Nobel peace prize.

But that prospect all but vanished with the referendum defeat, experts said.

"The Colombian peace treaty or anybody associated with it simply is not a candidate for the Nobel peace prize this year," said Kristian Berg Harpviken, director of Oslo's Peace Research Institute (PRIO).

The accord has now "lost legitimacy" to the point that it "is dead and cannot be implemented," said Maria Luisa Puig, a Latin America analyst at the Eurasia Group consultancy.

The FARC launched its guerrilla war in 1964, after the army crushed a peasant uprising.

Over the years, the conflict has drawn in several leftist rebel groups, right-wing paramilitaries and drug gangs.

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