France is braced for around 10 million visitors for the month-long football event which opens when the French take on Romania at the Stade de France on Friday. But it comes amid worries about a possible terrorist attack at the 10 large fan zones in host cities.
And there were ugly scenes on Thursday night in Marseille, where England play Russia on Saturday, as violence erupted between English fans and locals. One England supporter was injured and two arrested in the brawl that saw riot police use tear gas to disperse the crowds after trouble flared outside a pub.
According to reports, some fans were heard chanting: "Isis, where are you?"
“It as if we have created 10 open-air Bataclans and invited the jihadists to do their worst,” one French security source told The Independent.
The Bataclan concert hall was one of the targets of the three-pronged jihadist attack on the Paris area on November 13.
Ninety of the 130 people who died that day were killed by jihadists who fired automatic weapons into a crowd of rock concert-goers.
The organisers of Euros 2016 admit they considered scrapping the official zones where fans can mingle, watch games on giant screens and listen to pop concerts. They finally decided that the alternative was worse.
Jacques Lambert, Chairman of the Euro 2016 organising committee, said: “Everyone asked themselves the question.
"After examining the pros and cons, the host cities, the government and the organising committee all decided the same thing. It was better to host the fans in a secure area rather than let them wander about all over the place. The fan-zones will have exactly the same security as the match venues.”
Over the next month, 80,000 police and soldiers and 12,000 private security guards will be deployed to protect matches and the “fan-zones” from any repetition of the November Paris attacks.
In recent days, there have been 30 elaborate simulations by police and volunteers of terrorist assaults on stadia and fan zones. Simulations have included suicide bombings and random gun attacks on crowds.
The US and British governments and the French president François Hollande have all warned in the last fortnight that Euro 2016 is a tempting, potential target for Isis or other jihadist groups.
French security officials insist that intelligence has revealed no specific threat and has not picked up the trail of any terrorist group targeting the tournament.
All the same, with 2,500,000 ticket-carrying foreign fans certain to visit |France over the next month - and many more expected to travel without tickets – French authorities are on the highest possible alert.
“Even 100 per cent precaution cannot mean zero per cent risk,” said the interior minister, Bernard Cazeneuve.
A terror alert app has been created by French authorities to warn football fans in the event of attacks. The official mobile phone app, available for free in English and French, will warn fans of actual or imminent terror attacks and advise them where to seek aid or shelter.
The 10 fan zones are mostly in city centres. In Paris, most of the Champ de Mars beside the Eiffel Tower has been given over to a gigantic fenced area with a concert stage, bars and restaurants and one of the largest screens ever erected.
Up to 90,000 fans can be accommodated but will have to pass through six “security gates”.
The fan-zone in Marseille – first available for the England-Russia match on Saturday - is on the Prado beach on the southern edge of the city, near the Stade Velodrome football stadium.
Security there will include police launches and helicopters off shore. Swimming has been banned from 7pm until 5am on match days – but that is said to be mostly a precaution against fans drowning.
The French goverment has also banned the broadcasts of matches on giant screens outside cafés and bars. This was intended to reduce the risk of a repeat of another part of the November attacks – the machine-gunning of people on café terraces.
The junior minister for sport, Thierry Braillard, originally said that the ban would apply to all televisions outside bars. Officials later said the ban applied only to giant screens.