Colombian President Juan Manuel Santos won the 2016 Nobel Peace Prize on Friday for bringing to an end half a century of civil war.

In its citation, the Norwegian Nobel Committee paid tribute to Santos for concluding a peace accord with FARC guerillas. It said he began the process and made persistent efforts to move it forward despite knowing it would be unpopular.

"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," it said.

The committee noted that 13 million Colombian voters narrowly rejected the peace agreement in a referendum on Sunday. It said the result, in which 50.2% of voters turned the deal down, has cast "great uncertainty" over Colombia's future.

"There is a real danger that the peace process will come to a halt and that civil war will flare up again. This makes it even more important that the parties, headed by President Santos and FARC guerrilla leader Rodrigo Londono, continue to respect the ceasefire."

It noted that Santos has invited all parties to take part in a broad-based dialogue aimed at keeping the peace process alive.

"Even those who opposed the peace accord have welcomed such a dialogue. The Nobel Committee hopes that all parties will take their share of responsibility and participate constructively in the upcoming peace talks."