NEW YORK - Alex Jones, a prominent conspiracy theorist and the host of a popular right-wing radio show, has apologised for helping to spread and promote the hoax known as Pizzagate.

The admission Friday by Jones, host of "The Alex Jones Show" and operator of the website Infowars, was striking. In addition to promoting the Pizzagate conspiracy theory, he has contended that the Sept 11, 2001, attacks were inside jobs carried out by the US government and that the 2012 shooting at Sandy Hook Elementary School was a hoax concocted by people hostile to the Second Amendment.

The Pizzagate theory, which posited with no evidence that top Democratic officials were involved with a satanic child pornography ring centered around Comet Ping Pong, a pizza restaurant in Washington, grew in online forums before making its way to more visible venues, including Jones' show.

The prominence of the hoax drew attention to the proliferation of false and misleading news, much of it politically charged, that circulated on platforms like Facebook, Twitter and YouTube.

Jones made the apology to the owner of Comet Ping Pong, James Alefantis, on video, reading from a carefully worded statement that emphasised how widely the theory had spread before he weighed in on it.

He said that Infowars had "disassociated" itself from the story in December and had taken down the majority of broadcasts and videos that mentioned it. Jones also said that two reporters the show had worked with "are no longer with us," although he did not identify them or discuss the exact nature of their work with Infowars.

"To my knowledge today, neither Mr. Alefantis, nor his restaurant Comet Ping Pong, were involved in any human trafficking, as was part of the theories about Pizzagate that were being written about in many media outlets and which we commented upon," Jones said.

"We apologise to the extent our commentaries could be construed as negative statements about Mr. Alefantis or Comet Ping Pong, and we hope that anyone else involved in commenting on Pizzagate will do the same thing." The hoax has had real-world consequences. The pizzeria, Alefantis and his employees have been besieged by threats. Nearby businesses have also been affected. And the hoax has even spread to several other pizzerias around the country.

In December, police arrested a man, Edgar M. Welch, 28, a father of two from North Carolina, who they said showed up at Comet Ping Pong to investigate the claims and fired a semi-automatic rifle he had brought with him inside the pizzeria. Welch pleaded guilty on Friday to assault with a dangerous weapon and interstate transport of a firearm and will be sentenced in June, according to news media reports.

In an interview after his arrest, Welch told The New York Times that he listened to Jones' show, saying that the host "touches on some issues that are viable but goes off the deep end on some things." But the theory lives on. A small group of protesters showed up outside the White House on Saturday, holding signs that asked why the news media was covering up child trafficking and demanding an investigation into Hillary Clinton, Alefantis and John Podesta, Clinton's campaign manager, in connection with the hoax.

Alefantis said in an emailed statement that he was pleased with Jones' apology but wished it had come months ago.

"And his apology, while welcome, does nothing to address the harm he and his company have done to me, my business, and my community," he said. "That said, we can all hope that Mr. Jones' retreat is the beginning of a process to hold accountable the people who motivated an armed gunman to travel across state lines and fire his weapon in a family-friendly restaurant."