Brent crude futures fell by $14.25 on Monday to $31.02 a barrel, while US West Texas Intermediate (WTI) plunged $11.28 after the Saudi move to to $30 a barrel.
Saudi royal court guards wearing masks and dressed in black raided the homes of the senior royals on Friday morning. The detained men face treason charges, sources said.
Three seats short of majority, Benjamin Netanyahu is looking for defectors. Israeli press says potential deserters include Orly Levy-Abecassis, Omer Yankelevich, Orly Fruman and Amir Peretz.
While the World Bank pledged emergency funding for developing countries, the US central bank cut interest rates to cushion the virus impact on the world's largest economy.
Three major TV channels predict victory for Netanyahu. While the Likud party is set to win 36-37 parliamentary seats, the Blue and White will be reduced to 32-33.
Across China, the virus has infected nearly 60,000 people. Some 1,437 patients in the province are in critical state while 5,647 are in severe condition.