Barranquilla, Colombia - A US-backed lawyer who has never held public office narrowly won Colombia's presidential runoff Sunday, swinging the country hard right with a promise to wage war against drug-running guerrilla groups.

With almost all polling centers reporting, Abelardo de la Espriella won 49.66% of the vote versus left-wing Senator Ivan Cepeda's 48.7%.

The 47-year-old's victory extends a wave of rightist candidates who have swept to power across Latin America promising "iron fist" security policies.

"We are beginning a new era!" De la Espriella told supporters in the Caribbean city of Barranquilla from behind bullet-proof glass.

World US military kills two people and strands six in Caribbean boat strike

"For those who have sown violence, terror, drug trafficking, and corruption all these years, their time is up!" he said.

President Donald Trump and a host of right-wing leaders from across the Americas have clamored to offer congratulations and support.

After a campaign marred by guerrilla bomb attacks and the murder of a leading conservative presidential candidate, there was a quick sign of how tough it will be to unite the country.

As he was speaking, thousands of protestors gathered in Colombia's third-largest city Cali.

Some burned American flags, and others wielded bricks and bars and clashed with riot police, who tried to disperse the crowd with teargas.

China China announces new sanctions on US firms over Pentagon blacklist

But elsewhere there was elation. De la Espriella supporters poured onto the streets of several cities wearing the canary-yellow national soccer jersey he had adopted as a campaign uniform.

They waved flags, blew horns, and expressed hope that "The Tiger," as they call him, would bring security.

"I'm very happy," said 30-year-old supporter Daniela Oliveros in Barranquilla. "I believe a lot in the country, I believe a lot in freedom."

"Abelardo, at this moment, is giving us above all a sense of security, employment, and dignity," she said.

But with only a few hundred thousand votes separating the two candidates – De la Espriella also voiced a conciliatory tone.

"Mine will be an absolutely democratic government and a guarantor of freedom and institutional order," he said vowing to respect all races, religions, and political stripes.

"I will govern for all Colombians, for those who voted for me and for those who choose another candidate" he said.

De la Espriella's victory marks a return to power for Colombia's right wing, which has ruled for all but four of the last 200 years.

His victory is likely to test Colombia's fragile decade-old peace process.

During the campaign, the dual US-Colombian national who calls himself "El Tigre," told AFP that he would scrap peace talks with dissident groups and launch a 90-day campaign of US-backed airstrikes against them.

In the 10 years since a landmark peace accord was signed with FARC guerrillas, much of Colombia has prospered.

But cartels and dissident groups still control pockets of the country, cocaine exports are at an all-time high, and Colombia remains one of the world's most economically unequal countries.

"Colombia's best days are ahead," said US Secretary of State Marco Rubio, adding that Washington "looks forward to working closely with your incoming administration."

His opponent, 63-year-old leftist Senator Ivan Cepeda stopped short of conceding defeat, telling supporters he would wait until all the votes were validated.

"Once the count has been completed and its final result is known, and the corresponding checks have been carried out, we will acknowledge the official result," he said.

The preliminary vote must will now crosschecked before an official announcement is made. But to win Cepeda would need hundreds of thousands of votes to be overturned.

The margin of error for the first count is usually in the low thousands.

De la Espriella warned Cepeda to respect the democracy, form the opposition and "don't even think about stoking violence."

"The Tiger can still bite you harder than he has bitten you at the ballot box" he warned.

Cepeda's campaign had appealed to many worse-off Colombians who wanted a more equal economy and fear a return to violence.

"I'm very worried about what Abelardo might do in a government," said 40-year-old bank worker Santiago Galindo, who voted for Cepeda.

Galindo worried "how far his thirst for power could go and his willingness to trample over people without really caring about them."