Americans abroad warned of terrorism threat

WASHINGTON (CNN) -- The U.S. State Department advises Americans abroad to take special precautions based on reports that they could be targets of a terrorist threat.

The government has learned of a possible threat from extremists linked to Osama Bin Ladin's Al-Qaida organization, the State Department reported in issuing the worldwide caution, which expires on August 11.

"U.S. citizens are urged to maintain a high level of vigilance and to take appropriate steps to increase their security awareness to reduce their vulnerability," the announcement said.

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Americans should keep a low profile, vary their travel routes and times and be wary of mail and packages from unfamiliar sources. They also should avoid contact with suspicious objects and avoid leaving vehicles unattended when possible, the State Department said.

U.S. government facilities worldwide remain at a heightened state of alert, the announcement said, and some of those facilities may close or suspend operations if the need arises.

Saudi-born militant Osama bin Laden is wanted in the United States in connection with bomb attacks on U.S. embassies in Kenya and Tanzania in 1998. He lives in hiding in Afghanistan.