Colombia's leftist FARC rebel force signed a historic peace accord with the government Monday and apologized to the countless victims of the country's half-century civil war.

In an emotional open-air ceremony, President Juan Manuel Santos welcomed the communist rebels into the political sphere after signing the accord with FARC leader Rodrigo Londono, alias Timoleon "Timochenko" Jimenez.

Dressed in white, the former mortal enemies signed and shook hands, smiling before an audience of international dignitaries, drawing loud cheers.

The ceremony in the Caribbean coast city of Cartagena followed a four-year process to end the last major armed conflict in the Americas. The accord remains to be ratified by referendum in a week.

"We are being reborn to launch a new era of reconciliation and of building peace," Timochenko said.

"In the name of the FARC, I sincerely apologize to all the victims of the conflict for any pain we may have caused during this war."

Colombian authorities estimate the territorial and ideological conflict has killed 260,000 people, left 45,000 missing and uprooted 6.9 million.

"Let no one doubt that we are moving towards politics without weapons. Let us all prepare to disarm hearts and minds," Timochenko said.

Santos then addressed a message to the thousands of FARC fighters preparing to disarm in their jungle camps.

"When you begin your return to society... as head of state of the homeland that we all love, I welcome you to democracy," he said.

"Swapping bullets for votes and weapons for ideas is the bravest and most intelligent decision that any rebel group could take."

The 2,500 guests at the signing included UN Secretary General Ban Ki-moon, US Secretary of State John Kerry and the Vatican's Secretary of State Pietro Parolin.

Ban welcomed the agreement creating "conditions for a lasting peace."

An array of Latin American heads of state, including Cuban President Raul Castro, sat near the signatories on stage as the crowd waved white handkerchiefs and shouted "No more war!"

A squadron of planes flew overhead at sunset, prompting Timochenko to quip: "This time, they're coming to salute peace and not drop bombs."

- FARC's political future -

The FARC launched its guerrilla war against the Colombian government in 1964, after a peasant uprising that was crushed by the army.

Over the decades, the conflict drew in several leftist rebel groups, right-wing paramilitaries and drug gangs.

Under the deal, the FARC will now relaunch as a political party. Timochenko, 57, is expected to remain its leader.

At a remote jungle camp in El Diamante, western Colombia, FARC fighter David Preciado celebrated the accord by playing football with his comrades.

"The government did not defeat us, and we did not defeat them. Our 52 years of war were not in vain," he told AFP.

"We are aware that we have to move forward together, united... to finally achieve victory, giving power to the people by political means."

- Amnesty -

The rebels came to the negotiating table after being weakened by an army offensive led by Santos, 65, when he was defense minister.

After he became president, four years of talks hosted by Cuba yielded a final, 300-page accord last month.

It grants an amnesty for "political crimes" committed during the conflict, but not for the worst atrocities, such as massacres, torture and rape.

The FARC's fighters -- estimated by authorities to number more than 7,000 -- are to leave their mountain and jungle hideouts and disarm in a UN-supervised process.

- No to 'terrorists' -

Recent polls show the "Yes" camp in the lead to ratify the accord in a referendum on October 2.

But some Colombians resent the concessions made to the FARC.

Former president Alvaro Uribe led a demonstration against the deal on Monday.

"The Americans would not grant impunity to Osama Bin Laden. The French would not grant impunity to (Islamist militants) ISIS," he said.

"Why should we Colombians grant total impunity to terrorists?"

At the ceremony, Santos said: "I prefer an imperfect accord that saves lives to a perfect war that keeps sowing death and pain."

Kerry met with Santos on Monday and told the Colombian president that "a lot of hard work's been accomplished, but we have a lot of hard work ahead of us."

"The United States is very committed to being there with you, not just at the beginning... but now as people will look to see the result," he said.

The European Union suspended the FARC from its list of terrorist groups, EU foreign policy chief Federica Mogherini said in a statement.

The government has yet to begin planned peace talks with another, smaller leftist rebel group, the National Liberation Army (ELN), saying it must first stop kidnappings.

Timeline of the Colombia conflict
Cartagena, Colombia (AFP) Sept 27, 2016 - After half a century of conflict, the Revolutionary Armed Forces of Colombia (FARC) and the country's government signed a full peace accord on Monday.

Here are key dates in Latin America's longest armed conflict, which has killed 260,000 people according to Colombian authorities.

- 1964: FARC formed -

The government launches an offensive against communist groups in the center and west of the country.

On May 27, rebel commander Manuel Marulanda Velez flees the assault with 47 other men and forms the FARC.

- 1984: First peace bid -

On March 28, conservative president Belisario Betancur launches peace talks with the FARC under a bilateral truce.

The initiative breaks down in 1987 after right-wing paramilitaries assassinate a presidential candidate from a party allied to the FARC. Further peace efforts collapse in 1991 and 2002.

- 1996: Hostages taken -

On August 30, the FARC takes 60 Colombian soldiers hostage at a military base in the south.

The raid marks the start of its strategy of mass hostage-takings, which dominates the conflict over the following years.

- 2000: 'Plan Colombia' -

In June, the United States and Colombian president Andres Pastrana launch "Plan Colombia," a joint anti-narcotics strategy.

It is later broadened to include anti-guerrilla operations. Washington has spent more than $10 billion on arming and training Colombian forces.

- 2002: Betancourt captured -

In February, the FARC kidnap Franco-Colombian politician Ingrid Betancourt, a candidate for Colombian president.

During more than six years captive in the jungle, she becomes an international symbol of the conflict. She is rescued by the military in 2008.

- 2011: FARC leader killed -

The FARC's top commander, Alfonso Cano, is killed in a raid by the Colombian army on November 4.

Two other top leaders, Raul Reyes and Jorge Briceno, were killed in 2008 and 2010.

Cano is replaced by current leader Timoleon Jimenez, who reaches out to the government for peace talks.

- 2012: New peace talks -

On October 4, President Juan Manuel Santos's government launches new peace talks with the FARC, weakened by the loss of its top leaders.

- 2016: Peace deal -

On June 23, the FARC and the government sign a definitive ceasefire and disarmament agreement, a precursor to a comprehensive peace deal.

On September 26, they sign the full peace accord. It will be put to a referendum for ratification on October 2.