Saudi Arabia's stock market suffered a 6.8-percent drop on Sunday as the main indicator accumulated a fall of more than 500 points amid fears of imminent United States sanctions prompted by the disappearance of a Saudi journalist.

Journalist Jamal Khashoggi – a permanent resident of the US in self-imposed exile who penned a column in the Washington Post and was a fierce critic of Riyadh's human rights violations and of Crown Prince Mohammed bin Salman's policies – has been missing since he entered the kingdom's consulate in Istanbul, Turkey, on Oct. 2 to pick up the paperwork needed for his planned marriage.

This pronounced fall comes after US President Donald Trump warned on Saturday that his administration would inflict severe punishment on Saudi Arabia if the Middle Eastern kingdom was found to have played a part in the disappearance of the journalist.

Turkish media have widely reported that intelligence officials believe Khashoggi was murdered and dismembered inside the building by a Saudi hit squad, who may have removed the mutilated corpse in the consulate's diplomatic pouch, which is protected by international law from being searched by authorities.

Trump had previously said that even if the Saudis were to blame for Khashoggi's disappearance, he would not halt billions in arms sales to the country.

"I don't like the concept of stopping an investment of $110 billion into the United States, because you know what they're going to do, they're going to take that money and spend it in Russia or China," Trump said.