The U.S. State Department has issued a global travel alert for Americans traveling overseas, repeating an earlier warning of a heightened security risk in the wake of the raid that killed Osama bin Laden.

Department officials said Tuesday that Americans should take precaution and maintain vigilance about terrorist threats, demonstrations and the possibility of violence against U.S. citizens.

Administration officials believe al Qaeda and its affiliates are planning terrorist attacks as a form of revenge -- and they believe the attacks could be carried out before the 10th anniversary of 9/11.

The warning describes attempts by terrorists to attack American interests at home and abroad, including suicide attacks, assassinations, kidnappings, hijackings and bombings.

The department said Americans should consider the potential for attacks on transportation systems and tourist infrastructure and noted such attacks in Moscow, London, Madrid, Glasgow and New York in recent years.

The new notice also warns Americans about travel to certain countries in the Middle East and North Africa, where uprisings in recent months have the potential to turn violent.