Citing specific threats of attacks overseas from credible sources, the State Department warned Americans abroad to be especially vigilant during this week's anniversary of the Sept. 11 attacks and announced closings of several embassies so they can review their security postures.

State Department officials named embassies closed or set for closure in Lilongwe, Malawi; Abu Dhabi, UAE; Manama, Bahrain; Dushanbe, Tajikistan; Kuala Lumpur, Malaysia; Pnomh Penh, Cambodia; Hanoi, Vietnam and its consulate office in Ho Chi Minh City; Jakarta, Indonesia and its consulate in Surabaya; and Islamabad, Pakistan, as well as its Lahore, Peshawar and Karachi consulates. Karachi has been closed for several weeks due to insufficient setbacks from the road that expose it to potential car bombs. 

Six other embassies will be closed so employees can attend commemorative services, and four embassies are closed because of national holidays unrelated to the anniversary of the terror attacks.

State Department Spokesman Richard Boucher refused to explain why most of the closings are in East Asia rather than in the Middle East, though several of those countries do have large Muslim populations that may be hostile to U.S. interests.

"There's any number of factors involved here," Boucher said, adding that many of the embassies in the Middle East have taken so many precautions over the years that they are adequately fortified.

He said that many embassies decide on their own whether to close for security reasons.

On Monday night, the State Department warned Americans that "there is a continuing threat of terrorist actions, which may target civilians and include suicide operations."

It urged Americans to remain vigilant and exercise caution in their activities, particularly at clubs, restaurants, places of worship, schools and recreational areas, but to go about their business in any case.

"In many cases, terrorists do not distinguish between official and nonofficial targets, and in many cases, if they are looking at official targets and find them too well protected, they go looking for less well-protected targets," Boucher said Tuesday. "So the point we're trying to make is that there is a real threat on a global basis that Americans need to be aware of. Americans need to be careful and they need to be vigilant, they need to pay attention to their surroundings, but they need to go forth and do their business, at home or abroad, carefully but safely."

On Tuesday, the Justice Department announced that the United States was raising its domestic alert level to orange or a "high" level alert because of specific and credible threats of attacks overseas coupled with background chatter that looks eerily similar to conditions last Sept. 10.

Boucher said that just because Sept. 11 passes doesn't mean that Americans should stop being cautious or that anyone will be breathing a sigh of relief.

"This is just a reminder that there is a real threat to Americans on a global basis every day," he said.

Travelers who want to learn more about worldwide cautions can hear recorded information by calling (202) 647-5225, or can receive information by automated fax by dialing (202) 647-3000 from a fax machine.

Fox News' Teri Schultz and The Associated Press contributed to this report.