Davos, Switzerland (CNN Business) UN experts said they are "gravely concerned" by information they have received suggesting that a WhatsApp account belonging to Saudi Crown Prince Mohammed bin Salman was used to deliver spyware to the mobile phone of Amazon CEO Jeff Bezos .

"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 experts said in a statement Wednesday.

The statement was released by UN special rapporteur Agnes Callamard, who specializes in extrajudicial killings and conducted an investigation into the murder of Washington Post journalist Jamal Khashoggi, and David Kaye, a UN special rapporteur focused on freedom of expression. The pair called for an investigation into the allegations.

The UN experts released their statement after media outlets including CNN Business reported that a forensics team hired by Bezos had concluded that the CEO's mobile phone had been compromised and that the hack originated from an account controlled by bin Salman . A source told CNN that the forensics team had reached its conclusion with "medium to high" confidence. The story was first reported by The Guardian.

Saudi Arabia denied on Tuesday that it was responsible for any such hack. The Saudi embassy in Washington wrote on Twitter that "recent media reports that suggest the Kingdom is behind a hacking of Mr. Jeff Bezos' phone are absurd."

"We call for an investigation on these claims so that we can have all the facts out," the embassy added.

The UN experts said in their statement that they "recently became aware" of a forensic analysis of Bezos' phone which assessed that it was infiltrated on May 1, 2018, with a video file sent from a WhatsApp account utilized personally by bin Salman.

According to the assessment seen by the UN experts, a "massive" amount of information was exported from Bezos' phone starting within hours of the video being sent. The data spike continued undetected over some months and altogether, more than 6 gigabytes of data was stolen, according to the experts' summary of the report.

"The forensic analysis assessed that the intrusion likely was undertaken through the use of a prominent spyware product identified in other Saudi surveillance cases," the UN experts said in their statement.

A source close to the UN team said UN investigators did not have direct physical access to Bezos' phone but that they extensively vetted research done by FTI Consulting, the independent cyber security experts hired by Bezos. FTI Consulting declined to comment, citing client confidentiality.

Amazon AMZN Facebook FB Tuesday night, before the UN experts released their statement, Bezos declined through a representative to comment to CNN Business on the Guardian's story.declined to comment when contacted by CNN Business., which owns WhatsApp, did not immediately respond to a request for comment on the UN experts' statement; nor did a lawyer who represents Bezos.

On Wednesday, Bezos tweeted a photo of himself attending a memorial service for Khashoggi in 2019. The photo marked Bezos's first public remark since reports of the WhatsApp breach came to light.

The revelation casts a new shadow over the future king, whose efforts to overhaul Saudi Arabia's economy and attract foreign investment have been frustrated by global concern over his alleged role in the murder of Khashoggi in the country's consulate in Istanbul, Turkey. Sources previously told CNN that the CIA has concluded that bin Salman personally ordered the killing, which bin Salman has consistently denied.

At the time of his death in October 2018, Khashoggi was working as a columnist for the Washington Post, a newspaper owned by Bezos. Khashoggi, a dissident who had been critical of the Saudi government, began writing for the publication in September 2017 and published columns calling out repression in Saudi Arabia and the Saudi crown prince's grip on the country's media. In one column from early 2018, Khashoggi suggested the crown prince would benefit from "trying a little humility."

After Khashoggi's murder, the Washington Post began publishing articles about the role Saudi Arabia and the crown prince allegedly played in it. Bezos suggested in an online post published in February 2019 that he had become an enemy of Saudi Arabia due to the Washington Post's coverage of the murder.

The UN experts echoed that allegation on Wednesday.

"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," Callamard and Kaye said in their statement.

Bezos has also suggested that the phone attack was part of a scheme that allowed the National Enquirer, a US tabloid, to gain access to private texts he exchanged with a woman named Lauren Sanchez, with whom he was having an extramarital affair. The couple has since taken their relationship public.

A spokesman for the publisher of the National Enquirer previously said, "American Media does not have, nor have we ever had, any editorial or financial ties to Saudi Arabia." An attorney for American Media CEO David Pecker, Elkan Abramowitz, said in February that the source for the tabloid's story was "not Saudi Arabia."

CNN Business has previously reported that Lauren Sanchez's brother Michael Sanchez was the person who initially tipped off the National Enquirer. Michael Sanchez denied to the Washington Post that he played a role in leaking details about the relationship, and told CNN Business, "I have been told that the Amazon investigation determined that I was not involved in the leak of the d*ck pics, because I never had access to any of the d*ck pics."

Amazon CEO Jeff Bezos shown with Saudi Crown Prince Mohammed bin Salman.

Gavin de Becker, a security consultant working for Bezos, had previously suggested that Saudi Arabia played a role in the attack on the CEO's phone. "Our investigators and several experts concluded with high confidence that the Saudis had access to Bezos' phone, and gained private information," de Becker wrote in an opinion piece published by the Daily Beast in March 2019.

Saudi Arabia sentenced five people to death for the murder of Khashoggi in December but cleared a former top adviser to bin Salman, an outcome that Callamard described as "anything but justice." The UN expert previously found "sufficient credible evidence" that called for the Saudi crown prince to be investigated.

— Nick Paton Walsh and Brian Fung contributed to this article.