Stocks in Saudi Arabia tumbled amid investor worries of potential sanctions against the oil-rich country over the disappearance of journalist Jamal Khashoggi.

The Tadawul All Share Index closed 3.51% lower Oct. 14, dropping as much as 7% during the day, after U.S. President Donald Trump threatened "severe punishment" if Saudi Arabia is found to be connected to the disappearance of Khashoggi, a former government adviser and a critic of the kingdom, who has gone missing after entering a Saudi consulate in Istanbul on Oct. 2.

Saudi Arabia has denied any involvement in Khashoggi's disappearance. The country also warned that "if it receives any action, it will respond with greater action" in a Saudi Press Agency statement Oct. 14.

Brent crude oil futures rose 1.12% to $81.33 per barrel as of 2:24 a.m. ET.

Meanwhile, SoftBank Group Corp. shares closed 7.27% lower in Tokyo on concerns over the Japanese conglomerate's ties to Saudi Arabia and amid a recent market selloff. Saudi Arabia provided almost half of the funding for SoftBank's nearly $100 billion Vision Fund.

Saudi Arabia has also seen a growing number of attendees pull out from its Oct. 23 Future Investment Initiative conference due to Khashoggi's disappearance, Reuters reported. More business leaders and firms have been distancing themselves from the Saudis, including Virgin Group's Richard Branson, who had also suspended investment talks with Saudi Arabia's sovereign wealth fund.