US travel alert says Euro 2016 could be target

France's Olivier Giroud celebrates after scoring his team's second goal during a friendly match between France and Cameroon in Nantes on Tuesday. Photo / AP

The United States has warned its citizens about the risk of a terrorist attack during the Euro 2016 tournament, updating its travel advice on the same day that President Francois Hollande said terrorism was the biggest threat to the competition.

Hollande dismissed calls to scrap a controversial labour reform to save the games from chaos, saying the "biggest threat" to the football tournament in France was terrorism, not strikes.

Travel by train, air and road has been affected by a series of strikes in the country, which hosts the tournament from June 10 until July 10.

However, Hollande insisted that the main threat "remains terrorism", not strike action.

French intelligence recently warned of Islamists' desire to let off bombs in public places while security services have mounted several major training exercises in case of terror attack in train stations or stadiums.

Tourism industry representatives in the French capital and elsewhere have warned that the industrial action is seeing visitors cancel bookings en masse to the world's most visited city, only just recovering from a downturn in the wake of the November terror attacks.

"The scenes of guerrilla-type action in the middle of Paris, beamed around the world, reinforce the feeling of fear and misunderstanding," the tourist board said.

And today the State Department advised US citizens to be cautious.

"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 department said.

"We are alerting US citizens to the risk of potential terrorist attacks throughout Europe.

"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 State Department's advisory is part of a growing crescendo of warnings.

On Monday Hans-Georg Massen, head of German intelligence, said that they were picking up "quite a lot of background noise" from terrorists discussing the tournament.

"We know that (Isis) has the European Championship in its sights," he told Rheinische Post newspaper.

He added that while there was no hard evidence of an attack being planned, there was "quite a lot of background noise, an elevated number of indications" that Isis, al-Qaeda or its Syrian affiliate the Nusra Front wanted to perpetrate attacks against Western targets.

Britain's Foreign Office updated its travel advice, but only to add warnings about the potential strikes. The terrorist warning was already included in its advice.

"There is a high threat from terrorism," the FCO warned. "Due to ongoing threats to France by Islamist terrorist groups, and recent French military intervention against Daesh, the French Government has warned the public to be especially vigilant and has reinforced its security measures."