The State Department has issued a travel alert for all of Europe following Tuesday's terror attacks in Brussels, warning that "terrorist groups continue to plan near-term attacks throughout Europe."
State issues travel alert for all of Europe
The alert also warned tourists to "exercise vigilance when in public places or using mass transportation. Be aware of immediate surroundings and avoid crowded places. Exercise particular caution during religious holidays and at large festivals or events."
The Islamic State in Iraq and Syria (ISIS) claimed responsibility on Tuesday for the coordinated attacks, which left 31 people dead.
The warning comes as the Transportation Security Administration ramps up security at major U.S. airports in response to the attacks.
The State Department alert added that international efforts to counter the ISIS threat are ongoing.
"European governments continue to guard against terrorist attacks and conduct raids to disrupt plots," it said.
"We work closely with our allies and will continue to share information with our European partners that will help identify and counter terrorist threats."