Colombian President Juan Manuel Santos and the leader of the FARC rebels, Rodrigo Londoño Echeverri, alias "Timochenko," on Monday signed an accord to end 52 years of civil war in the Andean nation.

The pact is the result of nearly four years of talks in Havana and was signed at a solemn ceremony in Cartagena before more than 2,500 invited guests, including 15 Presidents and Spain’s King Juan Carlos, EFE news reported.

Timochenko was the first to put his signature to the document, using a bullet converted into a pen, meant to symbolise Colombia’s passage from conflict to peace.

The President also used a "bullet-pen" to sign the pact and then presented Timochenko with a dove pin for his lapel.

Smiling, the two men shook hands and exchanged a few words before accepting the congratulations of the dignitaries who joined them on the platform, including UN Secretary-General Ban Ki-moon and Cuban President Raul Castro and Norwegian Foreign Minister Borge Brende, whose countries have served as guarantors of the peace process.

Also present were the leaders of other nations that have supported the effort, such as Venezuela’s Nicolas Maduro, Chile’s Michelle Bachelet and Rafael Correa of Ecuador.

Santos and Timochenko initiated the agreement in August in Havana and Colombians will go to the polls on Sunday for a referendum on the pact.

The document establishes a timetable for the FARC to lay down their arms and become a legal political organisation, as well as an international verification mechanism to ensure that both sides fulfil their commitments.