The Euro 2016 soccer championship, which will be held in France from June 10 through July 10, could be a target of violent extremists, the U.S. warned Tuesday.

About one million fans from all over the world are expected to travel to France for the month-long event. But the U.S. State Department wants to make sure those venturing from America understand the risk of a potential attack on the high-profile event.

"Euro Cup stadiums, fan zones, and unaffiliated entertainment venues broadcasting the tournaments in France and across Europe represent potential targets for terrorists, as do other large-scale sporting events and public gathering places throughout Europe," the State Department said in a travel alert posted on its website. "France has extended its state of emergency through July 26 to cover the period of the soccer championship, as well as the Tour de France cycling race which will be held from July 2-24." 

The state of emergency was instated after last March's Islamist attacks in Paris.

The State Department also included security details about the Catholic Church's World Youth day, which is expected to draw as many as 2.5 million people to Krakow, Poland from July 26 to July 31.

"U.S. citizens should be aware that local infrastructure may be strained due to the large number of visitors," the State Department said. "Poland will impose border controls at all of its national borders from July 4 to August 2, and visitors to Poland during this period should be prepared to show their passport and undergo stricter security screening throughout Poland.  More information to help prepare for travel to World Youth Day can be found at and"  

The State Department also advised U.S. citizens traveling abroad to:

• Exercise vigilance when in public places or using mass transportation.
• Be aware of immediate surroundings and avoid crowded places.
• Follow the instructions of local authorities, especially in an emergency.
• Monitor media and local event information sources and factor updated information into your travel plans and activities.
• Be prepared for additional security screening and unexpected disruptions.
• Stay in touch with your family, have a plan if you are separated and ensure they know how to reach you in the event of an emergency.