"The American embassy in Riyadh advises all American citizens living in Saudi Arabia that it has received indications of operational planning for a terrorist attack or attacks in the kingdom," an embassy statement read out by an official said on Wednesday.
"The embassy has no specific information concerning timing, target or method of any possible attack(s)," the statement said.
The embassy advised US citizens to maintain a high level of vigilance and keep a low profile. 

Saudi Arabia has been battling a two-year wave of violence by loyalists to Saudi-born al-Qaida leader Osama bin Laden.

Ninety-one foreign nationals and Saudi civilians have been killed in the violence in the past two years, and damage has been estimated at more than $270 million, Saudi officials say.
More than 40 members of the security forces and 112 suspects have been killed in clashes.