Both moves coincided with the conviction of four men for their roles in the bombing of two American embassies in Africa in 1998.
In its "Worldwide Caution," the State Department said that Americans should "maintain a high level of vigilance" following the embassy bombing convictions, which mean possible death sentences for two of the four, all alleged associates of Osama bin Laden.
"In the past, such individuals have not distinguished between official and civilian targets. As always, we take this information seriously. U.S. Government facilities worldwide remain at a heightened state of alert," the statement read, although it added that the United States has not detected a specific threat.
"In addition, U.S. Government facilities have and will continue to temporarily close or suspend public services as necessary to review their security posture and ensure its adequacy," the caution read.
The United States has issued other worldwide cautions recently. One was called in October, 2000, after the bombing of the USS Cole in Yemen and that order was extended for five months in January.
Meanwhile, the Pentagon upgraded security at its naval headquarters in Bahrain and for some of its forces in Kuwait, because of a "reliable and specific threat," reports CBS News Correspondent Jim Stewart.
A defense official, who asked not to be identified, told Reuters American forces in the Gulf emirate, which is headquarters of the U.S. 5th Fleet, were put on alert over the weekend fter the information was received by intelligence sources.
"They had some threats in the area and Bahrain has been put on Threatcon (threat condition) Charlie," the official said. The level of alert is the second highest for U.S. forces behind Threatcon Delta. It requires base guards, troops and their families to be especially alert to possible attack.
The official declined to be specific about the threats, but stressed the information was received before the embassy bombings verdict. According to the Defense Almanac, a total of 949 servicemembers are in Bahrain, 734 of whom are in the Navy. Nearly 5,000 military personnel are based in Kuwait.
The embassy bombing verdict has raised rather than eased terrorism fears because the people convicted are low-level members of bin Laden's alleged terror network, which has been attacking American targets with grater frequency ever since allegedly masterminding assaults on U.S. troops in Somalia.
These acts have included an aborted plan to assassinate President Clinton in Manila, the embassy bombings, a failed plot to bomb millennial celebrations on the West Coast and the attack on the USS Cole.
The State Department Wednesday also cautioned against travel to Tajikistan and said protests in Sweden could get rough.
In Tajikistan, possible incursions by the Islamic Movement of Uzbekistan (IMU) prompted the State Department to advise Americans to "defer all travel to Tajikistan."
Similar threats in 1998 led to the suspension of operations at the U.S. embassy in the capital, Dushanbe. "Although the political climate has improved, the situation remains unpredictable," the department said Wednesday.
The department warned that Americans heading to Gothenberg, Sweden, "should exercise caution, avoid any crowds or demonstrations and monitor local media to keep informed" on protests that could accompany the European Union summit and World Summit On Sustainable Development to be held there June 14-16.
Up to 10,000 demonstrators are expected, and "as at past international meetings, there is a potential that some of the demonstrators may become disorderly or violent," the warning read.
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