JAKARTA, Indonesia -- Nine U.S. embassies in Asia, Africa and the Middle East were closed, and U.S. military bases and embassies in Europe enforced tightened security Tuesday, the eve of the anniversary of the Sept. 11 terror attacks.

In Washington, Bush administration officials cited the threats against U.S. embassies in southeast Asia in raising the nation's terror alert to "code orange," its second-highest level.

German authorities raided a trading company Tuesday that a German official said once employed a suspected al-Qaida recruiter accused of drafting members of the terror cell that dispatched the Sept. 11 suicide hijackers, and Turkey was on alert for the possibility that militants linked to al-Qaida might be planning poison gas attacks.

But the most direct threats were in Southeast Asia, where dozens of Islamic hard-liners allegedly linked to the al-Qaida terror network have been arrested over the last year in Singapore and Malaysia.

In Indonesia, the world's most populous Muslim nation and home to several hard-line Islamic groups, the U.S. Embassy announced it was closed until further notice because of a "credible and specific" terrorist threat.

"We know that the al-Qaida network is still far from defeated," Ambassador Ralph Boyce said. He implied the warning was received through intelligence sources, saying it was "more than an anonymous e-mail or a phoned in threat."

U.S. officials in neighboring Malaysia, a mostly Muslim country of 23 million people, said the embassy there would close until further notice due to a specific threat.

The American diplomatic mission in Cambodia will shut for at least three days as a security precaution. No details were given.

U.S. embassies were also closed in Vietnam, Pakistan, Tajikistan, Bahrain, the United Arab Emirates and Malawi.

In Europe, extra security was ordered at airports, government offices and embassies.

Italy assigned 4,000 soldiers to protect "sensitive sites," while Belgium ordered "strict vigilance" for its security authorities. German police said they were stepping up security at Frankfurt airport, continental Europe's biggest.

The U.S. State Department issued a worldwide caution this week urging Americans to remain especially vigilant, saying there was a "continuing threat of terrorist actions, which may target civilians and include suicide operations."

About 10 unarmed London police officers, backed by armed soldiers, were on duty at the U.S. Embassy on Grosvenor Square, where security has been stepped up for the anniversary.

U.S. diplomats said security also remained high at the embassy in Berlin, sealed off for a block on all sides by armed police.

The U.S. military's European Command, based at a sprawling headquarters in Stuttgart, Germany, and responsible for American forces in Europe and parts of Africa, said security measures were being kept at levels of recent months, but that base commanders could order extra measures as warranted.

Last week, German police acting on an FBI tip arrested a 24-year-old Turkish man and his fiancee, a U.S.-German citizen, on suspicion of planning to bomb U.S. military installations in Heidelberg. Investigators said they have no evidence linking them to al-Qaida and believe they were acting alone.

At the Spangdahlem U.S. air force base in western Germany, 12 buildings were evacuated for several hours Monday after an explosives-sniffing dog alerted authorities to a gravel truck entering the base. No bomb was found.

At London area airports, officials said airlines canceled 18 trans-Atlantic flights from Heathrow and at least two from Gatwick.

In France, Transport Minister Gilles de Robien warned that aviation "has become a weapon" as he toured Charles de Gaulle airport outside Paris to demonstrate extra security measures put in place since Sept. 11.

"At any instant, anywhere in France or in the world, terrorism can strike, and therefore, we are not free in the face of terrorism, we are on watch," Prime Minister Jean-Pierre Raffarin said in an interview with Radio France Internationale. "Monstrosity is always lying in wait, it's out there, and it is always possible."

With the al-Qaida network disrupted by the U.S.-led war on terrorism, European officials were warning of the threat of attacks by individual Islamic extremists who might act without outside direction.

The prosecutor who led the probe into Osama bin Laden's operations in Italy said the new threat to Europe in the aftermath of Sept. 11 comes from "free-lance" terrorists without direct connections to al-Qaida.

"At the moment, we are not threatened by the same network as before Sept. 11," Stefano Dambruoso told The Associated Press in an interview Monday night. "Al-Qaida as we knew it has been largely dismembered."

"But there are many frustrated Muslims in Europe, who live on the fringes of society. They are close to fundamentalist groups but don't belong to any organization."