The United States state department recently issued a travel alert to Americans for the risk of potential terrorist attacks in Europe this summer due to the huge number of tourists and high-profile events.

The warnings say that terrorists may be planning to "target major events, tourist sites, restaurants, commercial centres and transportation."

Said alert was released hours after French president, François Hollande, said that terrorism is still the biggest threat to the European Football Championship slated on June 10th-July 10th.

“The large number of tourists visiting Europe in the summer months will present greater targets for terrorists planning attacks in public locations, especially at large events,” warned state department, according to Breaking Travel News.

Stadiums, fan zones, and even unaffiliated entertainment venues that are broadcasting the tournaments in France and also across Europe may be potential targets for terrorists, as well as on other large-scale sporting events and public gatherings.

The state of emergency in France is extended through July 26 during the period of the championship and also to cover the Tour de France cycling race July 2-24, following the near-simultaneous attacks in the area that resulted in 130 deaths and many wounded citizens, BBC News reported.

The department said that US citizens who are visiting Europe during the period should be vigilant when in public places and when using mass transportation. They should also be aware of their immediate surroundings and avoid crowded places.

Aside from the sporting activities, the Catholic Church’s World Youth Day that will begin on July 26 in Krakow with an expected number of 2.5 million visitors is one event that they think will attract terrorists.

“I’m not aware of any specific, credible terrorist event around these events or in any particular place in Europe. This was issued ... based on an accumulation of information,” said John Kirby, spokesperson of the State Department, Guardian reported

Said travel alert will expire on August 31.