The US State Department has renewed its travel alert for Europe, warning citizens about the continued threat of terrorist attacks.
The latest update is an extension of the previous travel alert issued in May, and expires November 30.
American travelers are urged to exercise caution, particularly when visiting busy tourist locations, transportation hubs, markets, shopping malls and local government facilities.
Other soft targets include hotels, clubs, restaurants, places of worship, parks, high-profile events, educational institutions and airports.
Terrorist tactics include firearm attacks, explosives, the use of vehicles to ram into large crowds, and sharp-edged weapons that are difficult to detect prior to the attacks, says the state department.
The alert follows a steady string of terrorist incidents in France, Russia, Sweden, the UK, Spain and Finland, perpetrated by the ISIS.
"US citizens should always be alert to the possibility that terrorist sympathizers or self-radicalized extremists may conduct attacks with little or no warning," advises the state department.
In the event of an attack, citizens are advised to follow the instructions of local authorities, monitor media sources, stay in touch with family members and make sure they know how to reach you in the event of an emergency.
Visitors should also consult the website of the US embassy or consulate in their destination country.