A number of high profile business and media groups have pulled out of a top investment summit in Saudi Arabia in the wake of the disappearance and feared state-sanctioned murder of journalist Jamal Khashoggi.

Future Investment Initiative, nicknamed the 'Davos of the desert', is due to begin in the Saudi capital Riyadh on October 23, with speakers including JP Morgan Chase CEO Jamie Dimon and U.S. Treasury Secretary Steve Mnuchin.

Also listed as a speaker is Uber CEO Dara Khosrowshahi, who has now said he will not be attending unless the Saudi government come up with a plausible explanation for the Washington Post journalist's disappearance.

No thanks: Uber CEO Dara Khosrowshahi, left, and World Bank President Jim Yong Kim, right, are among those listed as speakers at Future Investment Initiative in Riyadh later this month who have pulled out in the wake of the disappearance of journalist Jamal Khashoggi

Missing: Washington Post writer Khashoggi, 59, is feared murdered by his own government, having last been seen entering the Saudi consulate in Istanbul last Tuesday

He said: 'I'm very troubled by the reports to date about Jamal Khashoggi. We are following the situation closely, and unless a substantially different set of facts emerges, I won't be attending the FII conference in Riyadh.'

U.S. mass media conglomerate Viacom Inc CEO Bob Bakish, and billionaire Steve Case, one of the founders of AOL, have also said said they were no longer going to Riyadh.

World Bank President Jim Yong Kim, who had been listed as a speaker, will not attend the conference, a World Bank official told Reuters on Friday citing a scheduling conflict.

CNN, the Financial Times, the New York Times as well as reporters and editors from the Economist and CNBC said they were no longer participating in the conference, which relied heavily on journalists to moderate top sessions.

This comes after British billionaire mogul Richard Branson suspended all business links with Saudi Arabia, including talks over a $1billion investment in Virgin Galactic.

Richard Branson (left) has suspended a $1billion investment project with Saudi Arabia amid rumors that the country had a hand in the disappearance of journalist Jamal Khashoggi (right)

'What has reportedly happened in Turkey around the disappearance of journalist Jamal Khashoggi, if proved true, would clearly change the ability of any of us in the West to do business with the Saudi Government,' Branson said in a statement Thursday.

'We have asked for more information from the authorities in Saudi and to clarify their position in relation to Mr Khashoggi.'

The Saudi government last year announced its intention to invest $1billion into Virgin Galactic and Virgin Orbit, which are under the umbrella of Branson's Virgin Group, according to CNBC.

Global pressure has mounted on Saudi Arabia, a close US ally, over the whereabouts of Khashoggi, who entered the consulate to get documents for his planned marriage last week.

His Turkish fiancee, Hatice Cengiz, who was waiting outside, said he never re-appeared.

Yesterday, a a witness claimed to have heard screams for help moments before Khashoggi disappeared from the Saudi consulate.

A source reportedly told The Washington Post Khashoggi was killed and then dismembered by members of security.

A demonstrator dressed as Saudi Arabian Crown Prince Mohammed bin Salman with "blood" on his hands protests outside the Saudi Embassy in Washington on October 8, 2018

'The voice recording from inside the embassy lays out what happened to Jamal after he entered,' the insider told the newspaper that Khashoggi, 59, worked for.

'You can hear his voice and the voices of men speaking Arabic … You can hear how he was interrogated, tortured and then murdered.'

TIMELINE: WHAT HAS HAPPENED IN MR KHASHOGGI'S DISAPPEARANCE OCTOBER 2 03:28: Gulf Stream IV private jet carrying suspected Saudi agents arrives at Istanbul airport. 05:05: The group checking into two hotels nearby to the Saudi consulate building. 12:13: Several diplomatic vehicles are filmed arriving at the consulate, allegedly carrying some of the Saudi agents. 13:06: Jamal Khashoggi is last seen on WhatsApp. He then hands his mobile to his fiancée Hatice Cengiz. 13:14: Khashoggi enters the consulate building. 13.24: A message is delivered to Khashoggi's WhatsApp – but it is never read. 15:08: Vehicles leave the consulate and are filmed arriving at the nearby Saudi consul's residence. 17:15: A second private jet carrying a number of suspected Saudi officials lands in Istanbul. 17:33: Khashoggi's Turkish fiancée, Hatice Cengiz, is seen on CCTV waiting outside the consulate. 18:20: One of the private jets departs from Istanbul airport. 21:00: The final plane leaves Istanbul. OCTOBER 3 The Washington Post, for whom Khashoggi writes opinion pieces, raises the alarm, saying Khashoggi has not been seen since he entered the consulate. OCTOBER 4 After an initial period of silence, Saudi Arabia says Khashoggi had disappeared 'after he left the consulate building'. *All times in Istanbul time. Advertisement

The audio reportedly holds the key to the 'gruesome' goings on that day but the Post reports the Turkish officials have been reluctant to release the recording as it may give away how they spy on foreign entities that are based there.

Recordings allegedly are very 'persuasive' in revealing the journalist was 'beaten' before various other details that have been shared with American officials took place. It's not clear if the US side has listened directly to the alleged evidence however.

On Thursday, the chairman of the US Senate Foreign Relations Committee said sanctions would have to be imposed at the 'highest levels' of the Saudi government if it were found that the government was behind the disappearance and reported death of Khashoggi, which Riyadh has denied.

'If it turns out to be what we all think it is today but don't know, there will have to be significant sanctions placed at the highest levels,' Republican Senator Bob Corker told reporters at the US Capitol.

Corker added: 'You can´t go around killing journalists.'

Further evidence that Khashoggi never left the consulate emerged today, as screenshots of his WhatsApp account shows he last used his mobile phone minutes before entering the building - when he was sent a link to a MailOnline article regarding a prominent Saudi.

The screenshots, obtained by NBC News, show the WhatsApp conversation between Khashoggi and a US friend, which indicated that the last time he was active on his phone was at 1.06pm Istanbul time.

Just eight minutes later, at 1.14pm, he was caught on CCTV as he entered the Saudi Arabian consulate.

The friend sent a message to Khashoggi at 1.24pm - a message which was received, but never read.

Khashoggi had been living in self-imposed exile in the US since late 2017, fearing arrest back home.

For years, the Saudi journalist was a modest voice for progressive change in the conservative Islamic kingdom.

Amid reports he was kidnapped or murdered inside the Saudi consulate, author and journalist John R. Bradley revealed Thursday exactly why the kingdom wants him dead.

In an article called for The Spectator, Bradley, who worked alongside Khashoggi at Saudi daily Arab News, reveals Khashoggi 'had dirt' on the kingdom's links to al-Qaeda before the terror attacks on September 11, 2001.