Colombia's President Juan Manuel Santos declared the country's 50-year conflict with FARC guerrillas "truly over" on Tuesday, as the last truckloads of decommissioned weapons rolled away to be melted down.

Santos himself shut a padlock on the last lot of decommissioned rifles before it was taken out of a remote demobilisation camp to formally seal the UN-supervised disarmament by the Revolutionary Armed Forces of Colombia (FARC).

"With the laying down of arms ... the conflict is truly over and a new phase begins in the life of our nation," Santos said at a ceremony in Pondores, a remote area in the northern Guajira department.

"This is truly a historic moment for the country," he said.

Colombia's Marxist FARC rebel group handed in more than 8,000 weapons and nearly 1.3 million pieces of ammunition as it demobilised after a peace deal with the government, the United Nations said.

"Our mission has, up to today, gathered 8,112 arms in these containers and destroyed almost 1.3 million cartridges," UN mission chief for Colombia Jean Arnault said at an event to mark the shipment. That is more weapons than the 7,132 the UN had originally reported in June

"This puts the country on the path to a new future," said Arnault.

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The weapons will be used to make three monuments celebrating the peace accord, agreed last year between FARC and the government of President Juan Manuel Santos, winner of last year's Nobel Peace Prize for his efforts to win an end to hostilities.

Roughly 7,000 FARC fighters have demobilised under the accord, which allows the group 10 unelected seats in Congress until the end of 2026 and grants amnesty to the majority of ex-fighters.

Rebels convicted by special courts of human rights violations will avoid traditional prison sentences, instead performing reparations work, such as removing landmines.

Al Jazeera's Alessandro Rampietti, reporting from Bogota, said another step for the FARC leadership will be to present a full list of their financial assets.

"This will be used to compensate the victims of the conflict. And it remains a contentious issue here since many Colombians fear they will not reveal all they have," he said.

"But leaders of the FARC insist that they will indeed completely fulfil all their obligations."

FARC's new name

The FARC was formed in the early 1960s by guerrillas affiliated with Colombia's communist party intent on resolving longstanding issues such as land disputes and government neglect of rural areas, issues that still resonate in much of the nation today.

Over the next five decades, the conflict between the rebels, government forces and right-wing paramilitaries claimed at least 250,000 lives and left another 60,000 people missing. Millions more were displaced from their homes fleeing the bloodshed.

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The handing over of rebel arms is a fundamental component of the peace accord, which also aims to reduce Colombia's booming coca production by encouraging farmers to grow food crops instead and expand the state's presence in remote areas where basic utilities like running water and electricity can be scarce.

The rebel leader known by the nom de guerre Ivan Marquez took advantage of the media attention on Tuesday's ceremony to preview what he said is likely to be the name of the former rebels' new political movement: the Revolutionary Alternative Force of Colombia, preserving the Spanish acronym, FARC.

"We will be part of the system, but raise our voice clearly and sharply against the system," Marquez said.