The U.S. State Department Tuesday issued a travel alert for citizens travelling to Europe following Tuesday's terrorist attacks in Brussels.

The travel alert, which expires on June 20, advised U.S. citizens to exercise vigilance when in public places or using public transportation.

"Terrorist groups continue to plan near-term attacks throughout Europe, targeting sporting events, tourist sites, restaurants, and transportation," the State Department said in a statement.



The U.S. also alerted citizens to be aware of immediate surroundings and avoid crowded places, and exercise particular caution during religious holidays and at large events.

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