It is another controversial choice for the prize committee in Norway, which rather optimistically chose Barack Obama in 2009 before he had even finished his first year in office.

But a Nobel committee spokeswoman defended the choice of Santos, saying she hoped it would "give him strength" to continue negotiations with Revolutionary Armed Forces of Colombia guerillas, known as FARC.

She also defended the decision to pick out the president from all the parties involved in the peace negotiations, saying he went "all in".

"The Norwegian Nobel committee wishes to encourage all those who are striving to achieve peace, reconciliation and justice in Colombia," the committee announced.

Mr Santos will receive an 8 million Swedish krona prize – about $1.2million.

He is still pushing to rescue the deal to end the 52-year conflict between the government and the rebels. In last Sunday's referendum Colombians voted by a slim majority of 50.21 per cent to reject a peace deal signed last month.

Opposition to the peace accord was partly a political protest vote from supporters of previous president Alvaro Uribe.

But there was also anger over the terms, which promised amnesty for former militants in exchange for a handover of weapons, and proposed they form a political party that was guaranteed a number of seats and could contest the next elections.

Mr Uribe said the rebels should be jailed instead.

The referendum result triggered a flurry of diplomacy, with a special UN envoy dispatched to Havana to try to reconvene peace talks.

FARC leader Rodrigo Londono, also known as Timoleon Jimenez or Timochenko, congratulated Mr Santos on the win.

Mr Londono has said he was prepared to "fix" the peace deal, and Mr Santos addressed the nation last week to assure them new negotiations would begin "as soon as possible [to] realise the dream of every Colombian to end the war with FARC".

"The country will come out winning," he said.

But the president's popularity has plunged during the week, with some calls for his resignation, and anger that he had called the referendum in the first place.

Previous peace prize recipients include Martin Luther King Jr, Malala Yousafzai, Mother Teresa, Nelson Mandela and Shimon Peres.

The committee said the award should also be seen as a tribute to the Colombian people who, "despite great hardships and abuses, have not given up hope of a just peace, and to all the parties who have contributed to the peace process".

They said  Mr Santos had initiated the negotiations that culminated in the peace accord, and "he has consistently sought to move the peace process forward.

"Well knowing that the accord was controversial, he was instrumental in ensuring that Colombian voters were able to voice their opinion concerning the peace accord in a referendum. The outcome of the vote was not what President Santos wanted: a narrow majority of the over 13 million Colombians who cast their ballots said no to the accord.

"[However] the fact that a majority of the voters said no to the peace accord does not necessarily mean that the peace process is dead... The Norwegian Nobel Committee emphasises the importance of the fact that President Santos is now inviting all parties to participate in a broad-based national dialogue aimed at advancing the peace process.

"By awarding this year's peace prize to President Juan Manuel Santos, the Norwegian Nobel Committee wishes to encourage all those who are striving to achieve peace, reconciliation and justice in Colombia. The president himself has made it clear that he will continue to work for peace right up until his very last day in office. The Committee hopes that the peace prize will give him strength to succeed in this demanding task."