The State Department warned U.S. citizens about the potential risks of travel in Europe after several attacks, including those earlier on Tuesday, March 22 in Brussels claimed by Islamic State, Reuters reports.

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

It urged U.S. citizens to be vigilant when in public places or using mass transportation, to avoid crowded places and to use extra caution during religious holidays and at large festivals and events.