The State Department is warning Americans visiting Europe this summer about the potential for terrorist attacks.
Tuesday's travel alert says major sporting events, tourist sites, restaurants and shopping centers are possible targets.
France is hosting soccer's European Championship and cycling's Tour de France, while under an extended state of emergency. Two-and-a-half million visitors are expected in Krakow, Poland, for the Catholic Church's World Youth Day in late July.
The department tells U.S. citizens to be vigilant in public places or when using mass transportation. They also should be prepared for additional security screening and unexpected disruptions.
Travelers leaving Logan Airport in Boston say that's exactly what they plan to do.
Alan Prouty, who is heading overseas, said, "We don't stay in too many crowds, that's good advice."
Maibritt Ljuntpeck, who is also heading overseas, said,"If there is terrorism around, we will stay away from big windows in a coffee shop, things like that."
The warning expires Aug. 31.