"In response to continued indications of operational planning for a terrorist attack or attacks in the kingdom, US military personnel stationed in Saudi Arabia have been instructed to suspend all non-duty related leisure travel outside of their work or housing stations," said a US embassy message.

The warden message, which went out late Monday and has been posted on the embassy's website, urged US citizens to "maintain a high level of vigilance".

It reiterated the embassy's statement last week that it has "no specific information concerning timing, target or method of any possible attack(s)".

The embassy said last Wednesday that it had "received indications of operational planning for a terrorist attack or attacks in the kingdom," where suspected Al-Qaeda militants launched a spate of bombings and shootings in May 2003, often targeting Westerners.

"The reason for the new warden message is to inform American citizens that this is the security posture of the US military," embassy deputy spokesman Andrew Mitchell told AFP on Tuesday.

He did not give more details.

According to Pentagon officials, several hundred US military personnel remained in Saudi Arabia after the US Air Force relocated its Gulf headquarters to the tiny neighboring emirate of Qatar in 2003, ending a 13-year presence in the kingdom.

The Prince Sultan Air Base south of Riyadh was once home to the largest US air operations in the region with a state-of-the-art command center, thousands of troops and squadrons of fighter jets, AWACS radar surveillance and tanker planes.

Pentagon officials said at the time that the military personnel staying behind would perform tasks such as training and tending to military sales.

All rights reserved. © 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.