Saudi Arabia on Sunday rejected any “threats” of economic sanctions or political pressure — a day after United States President Donald Trump’s comments on the disappearance of Jamal Khashoggi.

The statement carried by the state-run Saudi Press Agency also warned that the kingdom will respond to any steps taken against it.

This statement came after the Saudi stock market plunged by nearly 7 percent at one point on Sunday.

The statement did not directly acknowledge Khashoggi’s disappearance.

In an interview to be aired on Sunday, Trump told CBS' “60 Minutes”: “We're going to get to the bottom of it and there will be severe punishment”.

Business barons including British billionaire Richard Branson and Uber CEO Dara Khosrowshahi, as well as media powerhouses like Bloomberg and CNN, have pulled out of next week's Future Investment Initiative (FII) in Riyadh, dubbed "Davos in the desert".

'Baseless allegations'

Khashoggi, a Washington Post contributor, vanished after entering the consulate on October 2 to obtain official documents for his upcoming marriage.

Turkey on Saturday stepped up pressure on Saudi Arabia by accusing the kingdom of failing to cooperate with a probe into the journalist's disappearance.

Turkish officials have said they believe Khashoggi was killed inside the mission and claims have been leaked to media that he was tortured and even dismembered.

Saudi Arabia insists Khashoggi left the building safely and dismissed accusations that authorities had ordered his murder by a hit squad as "lies and baseless allegations".

The kingdom's Tadawul All-Shares Index (TASI) lost more than 500 points, diving by seven percent in the first two hours when trading resumed after the weekend, in panic selling reminiscent of the days after the global financial crisis in 2008.

It later clawed back some losses to close down 3.5 percent at 7,266.59 points.

The index had already dropped 3.0 percent on Thursday, following a rout on world stock markets fuelled by worries about higher interest rates and US President Donald Trump's attacks on the Federal Reserve.

Mohammed Zidan, market strategist at Thinkmarket in Dubai, said the drop in Saudi stocks was the result of panic selling because of several political and economic factors.

"There has been a kind of uncertainty surrounding the situation of the disappearance of Khashoggi which has caused the market to fall," Zidan told AFP.

"The withdrawal of top participants from the Riyadh investment conference has also negatively impacted traders' sentiment," he said.

Public relations crisis

The pullouts have cast a pall on the annual summit at which Prince Mohammed wowed investors last year with talking robots and blueprints for a futuristic mega city.

The withdrawal of Uber's Khosrowshahi from the event is particularly symbolic as the kingdom's vast Public Investment Fund (PIF) has invested $3.5 billion in the ride-hailing app.

Branson, who dropped two directorships linked to Saudi tourism projects around the Red Sea, said claims about Khashoggi's disappearance would "change the ability of any of us in the West to do business with the Saudi government".

Global multinational corporations "see potential in a developing market like Saudi Arabia, but for many the reputational risk of being associated with FII outweighs the potential gains from the Saudi economy", said Michael Stephens, a Middle East expert at the Royal United Services Institute.

Washington lobbying firm Harbour group which represented the Saudi government, has also terminated its $80,000 per month contract.

"We (have) ended the relationship," Richard Mintz, managing director of the firm, told AFP.

The Saudi leadership faces "an acute public relations crisis" over Khashoggi's disappearance, said consultancy group Eurasia.

"The leadership will now have to manage a more serious threat to its economic liberalisation strategy," Eurasia said.

"At this point, Saudi Arabia will find it incredibly challenging to contain the emerging crisis."