MIAMI, United States (AFP) — Authorities in North Carolina have decided there is not enough evidence to charge Donald Trump with incitement after one of his supporters punched a protester in the face at a campaign rally there last week.

Police launched an investigation into whether the Republican front-runner in the White House race could be charged with “inciting a riot” after a chaotic rally in the city of Fayetteville, where a white Trump supporter sucker-punched an African-American protester.

Critics say the billionaire businessman’s inflammatory rhetoric and barely veiled threats directed at protesters have been fuelling an increasingly toxic atmosphere surrounding his rallies.

But law enforcement officials said the violence in Fayetteville could not be blamed on Trump.

“The evidence does not meet the requisites of the law… to support a conviction of the crime of inciting a riot,” read a statement late Monday from the Cumberland County sheriff’s department.

“Accordingly, we will not be seeking a warrant or indictment against Mr Trump or his campaign for these offences,” read the statement, which comes after a few days of particularly violent clashes and protests at Trump events.

“While other aspects of our investigation are continuing, the investigation with regard to Mr Trump and his campaign has been concluded and no charges are anticipated.”

Violence erupted at a Trump rally in Chicago Friday that was called off in the face of mass protests, marking a sharp escalation in the tensions trailing the bombastic candidate who has called Mexicans rapists and urged a ban on Muslims entering the United States.

The Trump supporter who struck the protester, John McGraw, 78, has been charged with assault, battery and disorderly conduct.

McGraw, who later said that next time “we might have to kill him”, is due in court on April 6.

Trump said over the weekend he had told his campaign to “look into” paying McGraw’s legal fees, but sought to disown his comments yesterday.

“I don’t condone violence,” Trump told ABC television.

“Nobody has asked me for fees and I haven’t even seen it, so I never said I would.”

The Republican front-runner — along with the other remaining Democratic and Republican presidential contenders — faces another round of caucus and primary votes Tuesday which are expected to further pare down the field ahead of November’s general election.

The so-called “Super Tuesday 2” voting is being held in the states of Florida, Illinois, Missouri, North Carolina, and Ohio.