authorities have a security force of 90,000 during the tournament

Up to 82 workers hired to bolster security at Euro 2016 are on French terror watch lists, it has been claimed, as fears grow of an ISIS attack during the event.

French intelligence chiefs have screened 3,500 staff brought in to ensure the safety of fans at the tournament, which begins on Friday when host nation France takes on Romania.

The 82 people highlighted on watch lists could 'by definition' either belong to a terror group or have a background of 'questionable behaviour or extreme beliefs on either the left or right', it has been reported.

A security guard looks at the Euro 2016 fan zone, under construction on the Champs de Mars in Paris

French forensic officers take part in a mock terror attack drill outside the Stade des Lumieres, near Lyon earlier this week. The drill saw the officers looking over a fake crime scene that included dismembered bodies

French publication Le Point revealed the 3,500 recruits were screened by French intelligence agency the Directorate General of Internal Security, RT reports.

It comes after the head of the EU's law enforcement agency warned there is a 'high threat' of an ISIS terror attack at Euro 2016.

Europol director Rob Wainwright said last week he had 'no doubt' the football tournament would be a target for the terror group.

The U.S. government had earlier issued a travel alert to Americans, warning of the risk of potential attacks throughout Europe.

The State Department singled out the tournament, which will be held in France from June 10 to July 10.

Mr Wainwright, from Wales, said: 'I have no doubt that the Euros are on a potential target list for ISIS, for obvious reasons.

'That's a pretty obvious assumption. The threat is high, I think.'

But he said the the risk is 'not necessarily high' given the massive security operation set to be mounted by the French authorities.

Euro 2016 will take place amid an atmosphere of high alert following atrocities in Paris and Brussels.

French Police forces take part in a mock attack drill outside the Grand Stade stadium in Decines, near Lyon

French President Francois Hollande arrives to welcome Paraguay's President Horacio Cartes prior to their meeting at the Elysee Palace in Paris, Friday, June 3, 2016. (AP Photo/Francois Mori)

Last November, 130 people were killed when terrorists launched co-ordinated attacks on the French capital, targeting bars, restaurants and the national stadium, the Stade de France.

Then in March, 32 people died when Brussels was hit by suicide bombings at the airport and on the Metro.

French authorities have extended a state of emergency until the end of the tournament, as well as the Tour de France cycling race, which will be held from July 2 to July 24.

Some 2.5 million football fans are expected in stadiums, including 1.5 million foreign visitors.

Yesterday, French President Francois Hollande said that the threat of extremism won't stop the European Championships from being successful.

Hollande said in an interview on Sunday with France Inter radio that precautionary measures throughout the matches, including a 90,000-strong security force, will ensure the matches scattered in 10 French cities are safe.

Hollande said France decided to go ahead with Euro 2016 despite two waves of attacks last year, and make it a 'festival for people and for sports.'

But he said that spectators at the month-long tournament must accept security checks as they enter stadiums and fan zones.