The US State Department has issued a "potential terrorist attacks" warning for Americans planning to travel to Europe for events such as the Euro 2016 football tournament. The travel alert, which expires on 31 August, made no mention of specific threats to Euro 2016 matches or other events, but warned US citizens to "exercise vigilance" and "avoid crowded places". "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," the alert said. "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."

France's national stadium, the Stade de France, was one site targeted during the 13 November Paris attacks that left 130 people dead. Suicide bombers detonated explosive belts near gates at the stadium as France played Germany in a friendly match. France has already extended its state of emergency imposed after the attacks - through 26 July. It is expected that millions of football fans will descend on France, including record numbers from the UK, after England, Wales and Northern Ireland all qualified. In recent months, French special forces have been preparing to deal with simulated attacks during the tournament by carrying out several practice runs with emergency teams.

They carried out a drill at one of the busiest railway stations in Paris, and trained for a chemical attack, a hostage scenario or an attack on fans outside a stadium or watching matches on a big screen. The US State Department also warned Americans planning to travel to the Tour de France, which runs through 24 July. The Catholic Church's World Youth Day event between 26 July and 31 July in Krakow, Poland, was also noted in the travel alert. The event is expected to draw up to 2.5 million people, according to the State Department. The agency said US authorities are working "closely with our allies and will continue to share information with our European partners that will help identify and counter terrorist threats".