The State Department urged caution for Americans worldwide Monday, advising U.S. citizens traveling abroad to be vigilant for the remainder of the summer.

"This Worldwide Caution supersedes the previous Worldwide Caution of March 17, 2002, to alert Americans to the need to remain vigilant during the upcoming summer season and to remind them of the continuing threat of terrorist actions which may target civilians and include suicide operations," the State Department said.

"This Worldwide Caution expires on October 1, 2002," the agency said.

The warning cited the continuing threat of potential terror attacks that could target civilians, and the reference to suicide bombers was the first time such attacks have been mentioned in State Department warnings.

"The U.S. government continues to receive credible indications that extremist individuals are planning additional terrorist actions against U.S. interests. Such actions may be imminent," the warning said.

No specific target, timing or method is known to U.S. officials, the warning said, but Americans abroad should avoid clubs, restaurants, schools, or outdoor sporting events where fellow Americans gather because terrorists could choose them as a target.

Americans were urged to be more aware of their security while in crowds, avoid them or find other places that don't attract many Americans.

"Recent attacks on worshippers at a church and synagogue underline the growing possibility that as security is increased at official U.S. facilities, terrorists and their sympathizers will seek softer targets," the announcement said.

After five people, including two Americans, died in a grenade attack on a Protestant church in Pakistan March 17, the State Department issued a similar caution

On the home front, the FBI will protect major July Fourth parades and festivities as a precaution against a terrorist attack, U.S. officials say.

Although there is no known specific threat, the interrogation of detainees at the U.S. naval base in Guantanamo Bay, Cuba, revealed a general interest in Independence Day as a possible target, U.S. officials say.

The Associated Press contributed to this report.