The United States has closed its embassy and two consulates in Saudi Arabia for two days in response to a terror threat, the embassy has said.
US citizens in the country have been urged to keep a low profile, in the embassy’s second warning in a month.
Australia and Britain have also revised their travel advice because of “credible reports” of terror attacks.
But the Saudi authorities say they have no information of an imminent attack in the oil-rich kingdom.
The warnings, in what is the world’s largest oil exporter, have helped push crude oil prices to a new high.
“In response to a threat against US government buildings in the kingdom,” the US embassy in Riyadh and consulates in Jeddah and Dhahran were closing on Monday and Tuesday, the embassy said in a statement.
It reminded US citizens of previous attacks by militants on western compounds in the country, as well as kidnappings and assassinations of individual Westerners.
“US citizens are encouraged to maintain a high level of vigilance and to take appropriate steps to increase their security awareness,” the statement advised.
It suggested they “maintain good situational awareness” when visiting areas popular with Westerners as well as “keep a low profile” and vary times and routes of travel.
The embassy issued a similar warning on 20 July. It referred to “indications of operational planning” by Islamist militants, but said it had no information of a specific attack.
Regular gun battles
Australia and Britain have both posted warnings about travelling to Saudi Arabia on their websites.
“We have received credible reports that terrorists are planning attacks,” Australia’s Department of Foreign Affairs and Trade said.
The British embassy in Riyadh said it believed, “aviation interests remain a possible terrorist target.”
But Saudi Interior Ministry spokesman, Major General Mansour al-Turki, said they had no intelligence on a possible attack in the near future.
“We can’t dispel the possibility of a terrorist attack happening in the region,” he said. “But we have no information about an imminent terrorist attack in the kingdom.”
Militants loyal to Saudi-born al-Qaeda leader Osama Bin Laden have killed more than 90 foreign nationals and Saudi citizens and caused damage costing hundreds of millions of dollars since May 2003.
Saudi Arabia has come under pressure to curb extremism in the wake of the violence and there have been regular gun battles between Saudi security forces and militants.
The kingdom says it is doing everything in its power to crack down on individuals and organisations linked to terrorism.