The US state department on Wednesday advised nonessential American officials and their families in Saudi Arabia to leave.
Private US citizens should also consider leaving, it said.
Americans who travel to Saudi Arabia or remain there despite the warning were told to register with the US missions in the country.
"The US government continues to receive indications of terrorist threats aimed at American and Western interests," the department said.
"American citizens in Saudi Arabia should remain vigilant, particularly in public places associated with the Western community," it added.
Last month 17 people were killed and more than 100 injured when housing compound in Riyadh was bombed.