The US State Department is warning Americans who are travelling over the festive period to “exercise vigilance” in tourist areas due to the “heightened risk of terrorist attacks throughout Europe”.

The department’s travel warning said US citizens should “exercise caution at holiday festivals, events, and outdoor markets,” and stated that credible information indicates Isis, al-Qaeda and their affiliates are continuing to plan attacks in Europe and have a focus on holiday events.

"US citizens should also be alert to the possibility that extremist sympathizers or self-radicalized extremists may conduct attacks during this period with little or no warning,” it stated.

The State Department pointed to attacks that have already happened this year in Europe, referencing the assaults carried out in France, Belgium, Germany and Turkey.

Americans are urged to “exercise vigilance when attending large holiday events, visiting tourist sites, using public transportation and frequenting places of worship” as well as restaurants and hotels.

Isis has claimed a string of terror attacks in France and Belgium since January 2015 that have left more than 250 dead and hundreds injured.

The terrorist group has also indicated it will use the Thanksgiving holiday in America to target the Macy’s Thanksgiving Day Parade in New York City. It’s English language magazine, Rumiyah, called the parade an “excellent target”.