The U.S. State Department called on its citizens to assess the risks of traveling to Saudi Arabia given the August arrest of two terrorist cells in the country.
The travel advisory warned that "there remains an ongoing security threat due to the continued presence of terrorist groups, some affiliated with al-Qaida."
Several of al-Qaida operatives who carried out the Sept. 11, 2001, attacks on the United States came from Saudi Arabia.
"While the Saudi government has greatly improved the security environment throughout the kingdom since the major terrorist attack against foreign nationals in 2007, it is important to note that an ongoing security threat remains," the advisory stated.
There have been few reports of violence or major unrest in Saudi Arabia. A fuel truck crashed in Riyadh in early November, triggering an explosion that left at least 22 people dead.