The US State Department issued a Europe-wide travel alert to US citizens as Homeland Security Secretary Jeh Johnson stressed no ‘specific, credible intelligence’ suggested an attack on US soil is imminent.
Still, Johnson said the Transportation Security Administration would beef up security measures at major airports and rail stations in multiple cities with security screening delays inevitable.
US citizens in Europe were advised to ‘exercise vigilance’ in public places an on 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 twin terror attacks in Brussels, which claimed at least 34 lives, sparked an immediate security upgrade across the country.
The National Guard was deployed at JFK and LaGuardia airports and other locations in New York City, and major hubs Atlanta, Boston, Chicago, Los Angeles, Miami and Philadelphia are among the airports which have stepped up security both inside an outside terminal buildings.
Amtrak also announced a larger police presence at terminals.
Meanwhile Denver Airport has fully reopened after a section of the main terminal was evacuated yesterday when a suspicious package was found.
