The warning issued Wednesday said the timing and method of the potential attacks were not known.

.".. We have received credible information that an unidentified extremist(s) in Saudi Arabia may be planning to attack Westerners working and living in Al-Qassim, Saudi Arabia," the US warning said. Al-Qassim is an ultraconservative province northwest of Riyadh.

The embassy urged US citizens to "exercise prudence and enhanced security awareness at all times."