In Riyadh, Saudi Arabia, terrorists had the Seder Village compound under "active surveillance," the Embassy spokeswoman in Saudi Arabia, Carol Kalin, told The Associated Press by phone from the Saudi capital. She said other housing complexes may also be targeted.
Kalin said the embassy had barred its American employees and dependents from visiting housing compounds in Riyadh between the hours of 6 p.m. and 6 a.m. "except for official business."
"The Embassy continues to be concerned about the current security situation in Saudi Arabia, particularly the housing compounds in the Riyadh areas," Kalin said.
In the Kenyan capital, the U.S. Embassy said in a statement in Nairobi that, "The U.S. government recently received an anonymous warning detailing terrorist threats aimed at American and Western interests in downtown Nairobi ... the timing of the threat is within the next several days."
Kenyan Information Minister Raphael Tuju confirmed to The Associated Press that the government had information about a threat to two downtown hotels in Nairobi, saying "we're evaluating it and taking the necessary action."
The Barclay's Bank building was evacuated at midday after the KLM airline office received a phone call saying there was a bomb in the building, Patrick Kinyua, head of security for the building, said. Until this year, the building housed the U.S. Embassy public affairs office.
A second Barclay's branch office in downtown Nairobi was later evacuated when the manager received a similar threat.
Al Qaeda has twice struck Kenya. The old embassy was destroyed in 1998 by a car bomb, an attack that killed 219 people, including 12 Americans. Kenyan police reportedly uncovered a plot to destroy the new U.S. Embassy this past June.
There are some 30,000 Americans living in Saudi Arabia. The U.S. Embassy was scheduled to resume work Wednesday following a weeklong closure for a Muslim feast.
The Embassy's warning advises Americans in Riyadh to vary times and routes for essential travel, park vehicles in protected areas, check vehicles before use, and places and areas where Westerners are known to congregate.
Echoing the U.S. Embassy's advisory, Britain Tuesday backed the U.S. warning and also advised its citizens in Riyadh to "adopt a low profile."
"Following terrorist attacks in Riyadh in May and November, we continue to believe terrorists are planning further attacks in Saudi Arabia," said the Foreign Office, which has previously advised against all nonessential travel to the middle eastern kingdom.
Militants attacked three compounds for foreigners in Riyadh in May, detonating vehicle bombs that killed 35 people including the nine assailants. Another suicide attack killed 17 people in the capital on Nov. 8.