Spray-paint cans in hand, a generation of street artists is covering Colombia's run-down walls with rifles that shoot heart-shaped bullets and rainbow-colored pleas for peace.

After half a century of conflict, the end of which remains just beyond reach, war and peace have become central themes in Colombia's graffiti art.

On the streets of Bogota, corncobs that look like grenades and gun barrels sprouting carnations have provided the backdrop as the government and the leftist rebels of the Revolutionary Armed Forces of Colombia (FARC) worked for nearly four years to conclude a historic peace agreement.

The peace process suffered a shock setback Sunday when voters rejected the resulting accord in a referendum, apparently resentful of the blood shed by the Marxist guerrillas and the lenient punishment the deal meted out for their crimes.

But that only fueled the creative fire for people like DjLu, a graffiti artist known for dotting central Bogota with black-and-white messages of peace.

"I prefer a twisted peace to a perfect war," said the secretive artist.

DjLu, who prefers not to use his real name, doubles as an art professor at Catholic University of Colombia when he isn't out spray-painting public spaces as a self-described "servant of peace."

"I wanted to send a message that would open people's minds," he told AFP of his turn to politically charged graffiti a decade ago.

"I'm simply human, and as a human I think the conflict is absurd."

The prospect of turning the page on more than half a century stained by violence is increasingly fueling street artists' creativity in Bogota, where graffiti is surging as an artistic medium.

The city's mayor from 2012 to 2015, former guerrilla fighter Gustavo Petro, actively promoted graffiti as a public art form.

That stance helped counter the stigma of graffiti as vandalism, and giant murals sprouted up in iconic spots throughout the city.

- 'Political act' -

Today, visitors and fans can even take a graffiti tour, created by Australian expatriate Christian Petersen.

Not everyone is embracing the trend.

"Peace is in vogue... on the tourist stage that Colombia is becoming," said the street artist Stinkfish.

But Toxicomano ("Addict"), a graffiti artist known for works protesting atrocities committed by the Colombian army during the war, said the medium is well-suited to politically engaged art.

"The mere fact of painting in the street is a political act," said the artist, who painted a large, colorful mural urging Colombians to vote "yes to peace" in the run-up to Sunday's referendum.

The Colombian conflict has killed more than 260,000 people and forced nearly seven million to flee their homes. Another 45,000 are missing.

The government and the FARC began a ceasefire on August 29, and both sides appear committed to ending their fighting despite voters' rejection of the accord negotiated in the Cuban capital.

Seeking to save the peace process, President Juan Manuel Santos has dispatched his foreign minister, defense minister and chief peace negotiator to hold talks with the opposition.

They will be tasked with finding a compromise acceptable to both the FARC and the hardliners who led the campaign to vote against the Havana deal.

If they need inspiration, they can turn to the colorful messages of peace spray-painted on the nation's streets.