Colombia's Farc rebels have handed over a further 30% of its weapons to United Nations inspectors as part of last year's historic peace accord.
President Juan Manuel Santos said the gesture showed that the agreement with the rebels was going ahead as planned.
The Farc have now decommissioned 60% of the weapons they had registered with the UN.
Under the terms of the accord, the rebels have agreed to give up more than five decades of armed struggle.
"This is a historic day. Peace will be built little by little, like a cathedral, which you build brick by brick," said Mr Santos.
Analysis: Natalio Cosoy, BBC News, Bogota
It was not exactly the photograph many Colombians were expecting to see - but it is at least a photograph.
Up until now the story of the disarmament of the Farc had been only told with words: words from the rebel group, from the government and from the UN, who confirmed the weapons had been handed over and put in safe containers.
But now, finally, images of rifles, RPGs and pistols being checked and stored by a UN observer have been seen.
Some might still think that that is not enough, that the Farc should explicitly show how they renounce their weapons: they want photographs of fighters handing their rifles to the UN.
But the Farc insist that would be an image of defeat, one they do not want to convey. They insist they have reached a deal, not surrendered.
And many in Colombia believe today's image is more than enough.
He was due to attend the decommissioning ceremony in south-western Cauca region, but could not reach the area because of bad weather.
It went ahead with Farc leaders and UN officials at La Elvira, one of several transition zones where Farc rebels have been gathering before they are allowed to rejoin civilian life.
"We are totally committed to peace and will do all we can to help build this country we dream of," said a Farc leader at the event, Pablo Catatumbo.
The weapons are to be stored at 26 locations around the country.
Thousands of rifles and pistols need to be handed over before the Farc - the Revolutionary Armed Forces of Colombia - can become a political party.
Farc rebels have until 20 June to hand over the remaining weapons - a deadline that was extended from an original date of 30 May.
The peace deal was signed after four years of negotiations, held in Cuba.
It was initially rejected in a referendum last October, then reworked a month later and approved by Congress before beginning to be implemented.
For his efforts to reach peace with the Farc, Mr Santos was awarded last year's Nobel Peace Prize.