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LONDON — Two U.N. experts have called for an investigation into an accusation that Amazon founder Jeff Bezos, the world's richest man, had his phoned hacked after receiving a WhatsApp message from Saudi Arabia's crown prince, Mohammed bin Salman.

In a statement published Wednesday morning, David Kaye, the U.N. special rapporteur on freedom of opinion and expression, and Agnes Callamard, the U.N.'s special rapporteur on extrajudicial executions, wrote that there is a "reasonable belief" that the accusation has merit.

"The information we have received suggests the possible involvement of the Crown Prince in surveillance of Mr. Bezos, in an effort to influence, if not silence, The Washington Post's reporting on Saudi Arabia," the pair said in a joint statement, calling for further investigation.

They continued: "At a time when Saudi Arabia was supposedly investigating the killing of Mr. Khashoggi, and prosecuting those it deemed responsible, it was clandestinely waging a massive online campaign against Mr. Bezos and Amazon targeting him principally as the owner of The Washington Post."

Jamal Khashoggi, a Saudi journalist and a U.S. permanent resident, wrote critical commentaries in The Post about the kingdom and the crown prince. He was murdered in October 2018, and the CIA concluded that the powerful crown prince was behind the killing.

Amazon founder Jeff Bezos and Saudi Crown Prince Mohammed bin Salman posed for a picture Bezos' visit to Riyadh on Nov. 9, 2016. Saudi Royal Palace / AFP - Getty Images

The statement comes after Saudi Arabia dismissed the allegations, which first appeared in The Guardian on Tuesday night.

"We call for an investigation on these claims so that we can have all the facts out," the Saudi Embassy in Washington said. Saudi Arabia's foreign minister, Prince Faisal bin Farhan Al-Saud, said the allegation was "silly" and "absurd."

The U.N. officials' statement said technical experts had established a "medium-to-high confidence" that "Mr. Bezos was subjected to intrusive surveillance via hacking of his phone as a result of actions attributable to the WhatsApp account used by Crown Prince Mohammed bin Salman."

On May 8, 2018, the statement said, the encrypted message was sent from the crown prince to Bezos. "It is later established, with reasonable certainty, that the video's downloader infects Mr. Bezos' phone with malicious code," the statement said.

The evidence was gathered by a team of forensic experts in a protected environment, the statement said. Kaye said on Twitter that he and Callamard had "received" the analysis and then had independent experts look at the findings.

The statement also outlines how The Post published a series of columns by Khashoggi in the months leading up to the hack. Khashoggi was murdered and dismembered on Oct. 2, 2018, after entering the Saudi consulate in Istanbul. In December, Saudi Arabia sentenced five people to death for "committing and directly participating" in the killing.

The statement said the Saudi Royal Guard acquired spyware technology from the Herzliya, Israel-based NSO Group in November 2017, although the company strongly denies any involvement in the hack.

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"As we stated unequivocally in April 2019 to the same false assertion, our technology was not used in this instance," NSO said in a statement. "We know this because of how our software works and our technology cannot be used on US phone numbers."

The forensic analysis cited by the U.N. experts was commissioned by Bezos' security team and conducted by FTI Consulting of Washington, D.C., a source familiar with the case told NBC News.

The suspected May 2018 hack took place weeks after the crown prince paid a highly publicized visit to the United States, which included meetings with Bezos.

The Guardian's story alleged that Bezos' cellphone was hacked after he received the WhatsApp message from the crown prince, considered the power behind the Saudi throne. The Guardian said it obtained the leaked results of a forensic analysis that showed that it was "highly probable" that the hack was triggered by a corrupted video file sent from the crown prince's account.

An attorney for Bezos told The Guardian: "I have no comment on this except to say that Mr. Bezos is cooperating with investigations."

NBC News could not immediately reach Bezos' representatives for comment. Bezos' Twitter account sent a tweet Wednesday afternoon of a picture from a ceremony held for Khashoggi that Bezos attended.

The allegations come a year after details of Bezos' private life were leaked to the National Enquirer in January 2019. Bezos unexpectedly announced that he was to divorce his wife of 25 years, Mackenzie, the mother of their four children.

Hours after Bezos confirmed the split on Twitter, the National Enquirer posted a short story online revealing that the business mogul had been in a relationship with another woman, Lauren Sanchez. More lurid details later appeared online and in the subsequent print edition.

Meanwhile, Bezos launched his own investigation into how the information was leaked and alleged in a blog post that the leak may have been politically motivated.

The Saudi government, which is eager to attract investment from Western businesses, last year opened up the country to Western tourists for the first time.

Bezos, whose wealth is estimated to be more than $130 billion, visited Saudi Arabia in March 2018. Images released by the country's government at the time show him sitting alongside the crown prince, the pair apparently sharing a joke.

Crown Prince Mohammed, who has been on a drive to modernize his country's society and overhaul its oil-dependent economy, has been criticized for a deep crackdown on dissent in the kingdom. Khashoggi's murder put a damper on his international effort to publicize his modernization efforts.

Human rights advocates said the suspected hack is consistent with a widespread harassment campaign by Saudi Arabia's government targeting those who dare to criticize the regime.

tomorrow (wednesday) @AgnesCallamard & I will be releasing a public statement on this in which we address these very serious hacking allegations. https://t.co/X9NBrrwFnF — David Kaye (@davidakaye) January 21, 2020

"The allegation that the Saudi crown prince had a direct role in infecting Jeff Bezos' phone with sophisticated malware deserves investigation, yet it fits a well-established pattern of surveillance and harassment by Saudi authorities against critics at home and abroad," said Adam Coogle, a Middle East researcher for the nonprofit Human Rights Watch. "Lack of accountability for previous abuses means that it is possible, if not likely, that they will happen again."

Bruce Riedel, a former CIA officer who has written extensively about Saudi Arabia, said the alleged hack suggested that the crown prince appeared to be planning ahead.

"I don't know if they already knew they were going to kill Jamal Khashoggi, but apparently they knew they wanted leverage over The Post," said Riedel, now a fellow at the Brookings Institution.

The revelations also raised questions about whether U.S. intelligence agencies, which often monitor the phones of foreign leaders, were aware of the alleged hack, Riedel said.

Jeff Bezos, founder and chief executive officer of Amazon, arrives at an Economic Club of Washington discussion in Washington in September 2018. Bloomberg via Getty Images file

Sen. Chris Murphy, D-Conn., said he would write asking the director of national intelligence and the FBI to investigate whether the crown prince or other Saudi officials illegally gained access to Bezos' phone or the devices of other U.S. citizens or officials.

Murphy, a member of the Foreign Relations Committee, said he also was concerned about the reported communications of Jared Kushner, president's adviser and son-in-law, with Mohammed bin Salman.

"Given reports that Jared Kushner also frequently uses WhatsApp to communicate with Mohamed bin Salman, I have serious concerns for the massive national security vulnerabilities of that relationship," he said.

Kaye, one of the U.N. special rapporteurs who issued the statement Wednesday, said the hack represented "an attack on a fundamental democratic pillar of our country and other democratic countries."

"People should be really alarmed by these kind of allegations," Kaye said.

The U.N. officials presented their findings to the Saudi government several days ago, Kaye said.