Travelers should be cautious when using public transportation systems

The Department of State "encourages U.S. citizens living abroad or planning to travel abroad to enroll in the Clever Traveler Enrollment Program," the statement said. Officials use the program to contact enrollees in the event of an emergency.

Terrorist groups "continue to plan terrorist assaults against U.S. interests in multiple regions, including Europe, Asia, Africa, & the Middle East," a statement by the Department of State's Bureau of Consular Affairs said.
Travelers ought to be cautious when using public transportation systems, including maritime services like ferries, the statement said.
The Middle East & Africa are the most unpredictable areas, with terrorist groups & pirates attacking recently in Yemen, Algeria, Kenya & Somalia, the statement said.
It listed a variety of places that might be targeted, including "high-profile sporting events, residential areas, business offices, hotels, clubs, restaurants, places of worship, schools, public areas, & other tourist destinations."