Barranquilla, Colombia — A flamboyant U.S.-backed lawyer who has never held public office narrowly won Colombia's polarizing presidential runoff Sunday, swinging the country hard right and sparking violent protests.

With almost all the ballots counted, Abelardo de la Espriella held 49.66 percent of the vote versus left-wing Senator Ivan Cepeda's 48.70 percent.

The 47-year-old's slender win triggered demonstrations, but will ease ties with Washington and extend a regional right-wing wave centered on "iron fist" security policies.

"We are beginning a new era!" he told supporters in the Caribbean city of Barranquilla from behind thick bulletproof glass.

"For those who have sown violence, terror, drug trafficking, and corruption all these years, their time is up!" he said, echoing his vow to wage war against drug-running guerrilla groups.

President Trump cheered the result, exclaiming "He Won, BIG!" as a host of right-wing leaders from across the Americas clamored to offer congratulations and support.

But 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 for De la Espriella to unite this deeply divided nation.

As night fell, thousands of protestors gathered in Colombia's largest cities.

In Cali, some burned American flags as others wielded steel bars and clashed with riot police, who tried to disperse the crowd with teargas.

There was also unrest in the capital Bogota, where demonstrators burned tires and hurled bricks at police.

"We've already had many years of right-wing governments that care only about making the rich richer," 26-year-old student Natalia told AFP.

But elsewhere, there was elation.

De la Espriella supporters poured onto the streets of several cities wearing the canary-yellow national football jersey he'd 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.

De la Espriella strikes reassuring tone

With only a few hundred thousand votes separating the two candidates -- De la Espriella used his victory speech to try to calm his critics.

"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 added.

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

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

During the campaign, the dual U.S.-Colombian national told AFP he would scrap peace talks with dissident groups and launch a 90-day campaign of U.S.-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 U.S. Secretary of State Marco Rubio, adding that Washington "looks forward to working closely with your incoming administration."

Cepeda holding back on concession

His opponent, Cepeda, a 63-year-old leftist senator, stopped short of conceding defeat.

"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 told supporters.

For Cepeda to win, hundreds of thousands of votes would need to be overturned in a final count. The margin of error for the first count is usually in the low thousands.

No recount has ever overturned the results of any presidential election in Colombia, The Associated Press points out.   

De la Espriella warned Cepeda to respect the vote, form the opposition and not to "even think about stoking violence."

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