France on high terror alert: 4 things you need to know ahead of Euro 2016

With matches spread across 10 venues in nine cities, the country is undeer a state of emergency and security forces have launched an enormous operation to prevent any repeat of the jihadist attacks in Paris last November.

Here are the stakes:

Some 77,000 police and paramilitary police will be deployed, along with 13,000 private security guards to secure venues and public fan zones.

This week, Paris police chief Michel Cadot said an extra 3,000 officers were being added to the 10,000 allotted for the capital.

In addition, some of the 10,000 soldiers deployed around the country since last year's attacks will also be used.

Security inside stadiums is the responsibility of UEFA, while safety at "fan zones" which could gather up to 90,000 fans outside stadiums will be in the hands of private security companies.

Suicide bombers tried unsuccessfully to gain entry to the Stade de France in the November 13 attacks on Paris so security forces are leaving nothing to chance.

An additional 2.40 metre (7ft 10ins) perimeter fence has been added to the stadium for the tournament.

Police and health workers have run practice drills, including a mock gun and explosives attack at the Stade de France last week, and a simulated chemical and biological weapons attack at the Lille stadium in April.

Islamic State (IS), which claimed responsibility for the November attacks on the capital that killed 130 people, has designated France a leading target.

President Francois Hollande acknowledged the risk on Sunday. "This threat exists, but we must not be daunted," he told French radio.

Britain warned its citizens Tuesday that there is a "high threat from terrorism" at the tournament and warned people to be "vigilant" at stadiums, fan zones and transport hubs.

The US State Department released a similar statement last week, adding that "unaffiliated entertainment venues broadcasting the tournaments in France and across Europe" were also potential attack targets.

However, France's Interior Minister Bernard Cazeneuve has said there is no knowledge of a particular plot.

"At this time we do not have a specific threat to a specific team or a specific player, a specific match, or a specific fan zone," he said last month.

A new dimension was added Monday when Ukraine said it had arrested a suspected far-right French extremist with an arsenal of weapons, including 125 kilogrammes of TNT, who was allegedly planning attacks on Muslim, Jewish and government targets in France during the tournament.

The November attacks demonstrated that jihadists were willing to hit random "soft targets" such as bars and restaurants.

Experts say jihadists could aim for areas with minimal security protection during Euro 2016.

"You protect 1,000 targets, so it's the 1,001st target that will be hit," said Pascal Boniface, of the Institute for International and Strategic Relations in Paris.

France implemented "Operation Vigipirate" emergency measures after the jihadist attacks on Charlie Hebdo magazine and a Jewish supermarket in January 2015, with 10,000 troops deployed at sensitive locations such as tourist spots and Jewish sites.

Following the November attacks, a state of emergency was declared, allowing police to raid homes and hold people under house arrest with minimal judicial oversight.

It was extended for a third time in May, to cover Euro 2016 and the Tour de France cycle race in July.