The Washington Post reported in recent days that the Turkish government informed USA officials it was in possession of video recordings that prove Khashoggi was killed inside the consulate, but have not made them public.
That's right Mark... the foreign ministers of Britain, France and Germany released a joint statement on Sunday saying they treating the case with "the utmost seriousness".
"If, as they say, this awful murder didn't happen then where is Jamal Khashoggi?".
He told CBS: "We're going to get to the bottom of it".
For the moment, suspicions about Saudi Arabia's role in Khashoggi's disappearance have tainted the reformist image carefully cultivated by Crown Prince Mohammed.
"The Kingdom affirms its total rejection of any threats and attempts to undermine it, whether by threatening to impose economic sanctions, using political pressures, or repeating false accusations that will not undermine the Kingdom and its staunch positions and Arab, Islamic and worldwide status", the ministry added.
UK Foreign Secretary Jeremy Hunt said that whatever happened now was "absolutely up to Saudi Arabia".
A Saudi official source quoted by SPA news agency said it was "a positive move" Turkey had agreed to the creation of what it described as a "joint action team" over Khashoggi's disappearance.
On Sunday, Trump threatened "severe punishment" against Saudi Arabia if it turns out Khashoggi was killed in the consulate, though he also cautioned Washington would be "punishing" itself if it scrapped any military sales to Riyadh.
A Turkish police officer secures the entrance to Saudi Arabia's consulate in Istanbul, Sunday, Oct. 14, 2018. Saudi officials said the allegations are "baseless", but have offered no evidence Khashoggi ever left the consulate.
By the close, the market had recovered some of its losses, ending down 3.5 percent. Uber's CEO has also backed out, while billionaire Richard Branson has suspended talks with Riyadh regarding a planned $1 billion investment into his space ventures.
Saudi stocks dropped as much as 7 per cent, the most since 2014, on concerns that relations with the United States may sour, before trimming losses to close 3.5 per cent down.
Earlier in the day, Ford Motor Chairman Bill Ford has also cancelled an upcoming trip to the Riyadh business conference.