Saudi Arabia's stock index fell 3.8 percent in the opening minutes of trade on Tuesday, largely reversing its 4.1 percent rebound on Monday.
The market has been volatile for several days because of concern that international outrage over the disappearance of dissident journalist Jamal Khashoggi could hurt inflows of foreign investment.
U.S. Secretary of State Mike Pompeo arrived in Riyadh on Tuesday to discuss the affair.