The U.S. has issued a worldwide travel alert ahead of the 10th anniversary of the Sept. 11 attacks. The alert cautions Americans about the continued threat posed by al-Qaida and other groups.
The State Department isn't citing any specific threats to the United States that have been identified from al-Qaida or its allies.
But the department says U.S. citizens living or traveling abroad should take precautions because terrorist groups can attack anywhere.
Friday's alert notes that previous attacks were planned for significant dates, presumably to gain maximum public attention.
The U.S. says Americans abroad should register on the State Department's website or at an embassy or consulate. This makes it easier for embassies to reach people in case of emergency.