The attack could occur “in the near future,” according to a State Department announcement issued Thursday.

“While we cannot certify the credibility of the threat, in light of recent events this information is being shared with the American community,” the statement said.

The threat specifically mentioned Jeddah’s Al-Hamra district, an area where some US Consulate workers and their families live. Those families have “relocated to different quarters.” Jeddah is about 525 miles west of Riyadh.

One senior State Department official said the information came in a phone call but said it has not been “corroborated.”

Following Monday’s near-simultaneous suicide bombings, the official said, “We’re all over anything that says Saudi Arabia.”

Yesterday mid-afternoon a security alert which turned out to be a bomb scare happened at Jeddah Islamic Port, but an American Diplomat said it turned out to be nothing.

Police are on high alert in the Al-Hamra district in Jeddah, where jeeps in groups of two or more can be seen patrolling the area armed with AK-47 rifles.

Police are also patrolling the area on motorcycles in groups of two, particularly near the many consulates in Mohammed Bin Abdulaziz Street, stopping cars for random checks. Security was beefed up here at a major compound which houses the Saudi and expatriate staff of Saudi companies and their families just hours after the Riyadh blast.

However, with the new advisory issued within the last 24 hours, Saudi military personnel armed with truck-mounted 50-caliber machine-guns have been posted at most compounds housing Western expatriate workers. In addition, cement barriers have been placed on the roads approaching the compound entrances forcing vehicles to slow to a crawl.

At one Jeddah compound, bollards — mechanical steel posts that rise out of the ground — which had been in place for some time, were actually being used. Security guards and patrols have been tripled, and Jeddah police cruisers were parked at the main entrance, while others patrolled the perimeter.

Every vehicle stopping alongside the compound’s exterior walls is immediately investigated by armed police officers.

The security manager for the compound told Arab News: “It’s business as usual for the residents of the compound, but from a security standpoint, I prefer that the names of the compounds in my charge aren’t mentioned in the article. I don’t want to draw unnecessary attention to them.”

An Irish resident told Arab News: “Our thoughts are with the victims and their families. I can’t imagine the horror they’ve experienced. Of course I worry about such a thing happening in Jeddah, but what are we expected to do, quit our jobs, and pack up and go back home? That’s what I think the terrorists want, and I’m not going to let them have it.”