Saudi Arabia, the world's biggest oil exporter, said on Sunday it would retaliate against any punitive measures with even "stronger ones", according to a statement carried by the official Saudi Press Agency.
Still, regional traders said speculation the Khashoggi case might deter some inflows of foreign investment - and that a backlash in the US Congress could lead to US sanctions against some Saudi individuals - had triggered panic selling of stocks by some local investors. American lawmakers have threated sanctions against the Saudis, and Germany, France and Britain jointly called today for a "credible investigation" into Mr Khashoggi's disappearance.
Khashoggi, a Saudi national and US resident, entered the Saudi consulate in Istanbul, Turkey, on October 2 and never returned.
"Germany, the United Kingdom and France share the grave concern expressed by others including HRVP [Federica] Mogherini and UNSG [Antonio] Guterres, and are treating this incident with the utmost seriousness".
However, Turkish Foreign Minister Mevlut Cavusoglu said on Saturday that Saudi authorities were not cooperating with the investigation into the disappearance of Saudi journalist Jamal Khashoggi, and in particular are not letting Turkish prosecutors into the consulate building.
An investment conference seen as a platform for the crown prince due to take place next week in Riyadh and dubbed "Davos in the Desert", has been hit by a string of prominent cancellations.
"By week's end, The New York Times and every other major Western news media organization, except Fox Business Network, had canceled its participation", the Times reported.
Cengiz, a doctoral student at a university in Istanbul, wrote: "If the allegations are true, and Jamal has been murdered by the errand boys of Mohammed bin Salman, he is already a martyr". Despite being anxious for his safety, he had gone into the consulate in Istanbul to get a document necessary to marry his Turkish fiancee, his fiancee and friends have said.
In an interview to be aired Sunday, Trump told CBS' "60 Minutes" that "We're going to get to the bottom of it and there will be severe punishment". "When we arrived at the consulate, he went right in".
The king thanked Mr Erdogan for welcoming a Saudi proposal to form a joint working group to discuss Mr Khashoggi's disappearance and said no one could undermine their relationship.
"I had planned a party, inviting his closest friends to surround him with the love and warmth that he had missed", she wrote.
After committing $45 billion to the Vision Fund, Saudi Arabia's crown prince Mohammed bin Salman also pledged to invest billions in SoftBank's next venture capital fund.
But rather than a dissident, he saw himself as a patriot "using his pen for the good of his country", she said. But she said, "If he makes a genuine contribution to the efforts to reveal what happened inside the Saudi consulate in Istanbul that day, I will consider accepting his invitation".
The kingdom has appointed Son as an advisor for its planned $500 billion NEOM high-tech city, and in October past year, it said it was considering selling a large stake in Saudi Electricity Co to the Vision Fund.