American travelers headed to Europe were met with a stern warning from the US State Department. The new advisory said Islamic radical attacks are highly likely in almost any country in Europe.

The US State Department's announcement, according to Express UK, warned about possible attacks and activities of terrorist sympathizers and "self-radicalized extremists" who could attack crowded areas in the cities of different European countries. The US State Department explained that no clear or threat of a terrorist attack has been made, but it's likely during summer holidays when different European tourist spots become crowded.

Several French extremist attacks had prompted the French government to tighten its security further. Former French Prime Minister Francois Fillon was the target of a foiled attack by authorities the previous month. Another attack in Paris' Champs-Elysee saw a terrorist open fire against crowds before authorities had apprehended him.

The new advisory saw an increase in American outbound airport security to the point that the US State Department urged travelers to enroll in its Smart Traveler Enrollment Program (STEP) with the perks of faster security screenings through advanced background and security checks. The program also features faster luggage inspection for rushing travelers.

U.S. inbound passengers from Europe were disallowed to hand-carry their laptops, causing great hassle to European travelers. The laptop ban in airplane cabins had delayed many Middle Eastern travelers headed into the U.S. as well.

According to The Independent UK, Britain's Top Terrorism Legislation Reviewer Max Hull said in February that Britain faces possible terrorist attacks from the Islamic State with risks higher than the IRA's likelihood of attack in the 1970s. Britain was also a target of an extremist-related attack in Westminster in March, leaving the British terror level to "severe."