As fans await Friday’s kickoff of the 2016 UEFA Euro soccer tournament – among the most anticipated and popular sporting events in Europe – French officials are bracing for the worst.

Hosted in France this year, the matches begin seven months after attacks by Islamic State militants that left 130 dead across Paris. The tournament will also officially open at the Stade de France, the same venue where militants detonated suicide bombs in November.

Since the attacks, an official “state of emergency” has remained in effect. But many people wonder whether French authorities have done enough to stop another terrorist strike.

For many observers – including the U.S. and British governments – the tournament presents a major target for Islamic State and al-Qaida operatives: hundreds of thousands of spectators packed in enclosed spaces, and an anticipated audience of billions watching live around the world.

Authorities believe that the same terrorist cell of Islamic State militants that attacked Paris in November and Brussels in March had initially planned an attack on Euro 2016.

After the Brussels attacks, Mohammed Abrini, the so-called “man in the hat” seen in surveillance footage at Brussels Airport before his companions detonated suicide bombs, told investigators that Euro 2016 had been the group’s ultimate target.

In late May, a recorded message attributed to Abu Mohammed al-Adnani, the official spokesman for the Islamic State, threatened a “month of calamity” for Western “nonbelievers” during the Muslim holy month of Ramadan, which started Sunday and ends July 5.

The message also urged European Muslims to carry out attacks on European civilians.

Both the State Department and Britain’s Foreign Office have issued travel alerts for citizens attending the tournament. “Credible information indicates terrorist groups continue to plot possible attacks in Europe,” the State Department warned Tuesday.

In an interview, Jean-François Martins, who is in charge of tourism and sports for the French capital as a special assistant to Paris’s mayor, Anne Hidalgo, said authorities have taken every possible precaution.

“Each weekend in France, we have a football game,” he said. “We know how to do it.”

“We are doing everything to prevent a terrorist attack, and we are also equally preparing ourselves to respond to one,” Bernard Cazeneuve, France’s interior minister, told reporters earlier this month.

But a trial run at the Stade de France late last month painted a slightly different picture: fans were able to overrun security, as well as enter the stadium with prohibited devices such as fireworks and smoke bombs.

On Monday, Ukrainian authorities announced the arrest of a 25-year-old Frenchman on charges of attempting to smuggle firearms and weapons into France for a series of attacks allegedly planned for the month of the tournament.

According to Ukrainian security officials, the suspect – later identified only as Grégoire M. – had amassed 275 pounds of dynamite, two rocket-propelled grenades, five Kalashnikov rifles, more than 5,000 cartridges and 20 balaclavas.

The suspect, from the Lorraine region of eastern France, was described as an “ultra-nationalist” by Ukrainian authorities, apparently seeking revenge against the massive influx of predominately Muslim migrants and refugees into Europe in recent years.

In 2015 alone, more than 1 million people arrived in continental Europe, many of them from war-torn Syria and Iraq. Two who later would detonate suicide bombs outside the Stade de France first masqueraded as asylum seekers.

French investigators on Tuesday disputed the Ukrainians’ account of a terrorist plot, telling Reuters that the suspect was more likely involved in a smuggling operation.

In any case, the month-long tournament presents a formidable security challenge.

Unlike the Olympic games – typically held in one urban area – the Euro tournament takes place at venues in 10 different cities across France. Fifty-one games will be played between June 10 and July 10.

About 100,000 security personnel will be deployed to guard the sporting venues.

According to Martins, the 2015 terrorist attacks have led to extra security precautions, especially for so-called “fan zones,” large enclosures where fans can watch the matches on large screens without having to buy tickets.

In Paris, the fan zone will be at the base of the Eiffel Tower, an area of more than 32 acres where approximately 92,000 fans are expected to turn out, Martins said.

The extra security precautions there will include, most prominently, a heightened police presence, with approximately 1,500 police and security officers on hand – roughly one officer per 65 fans. Metal detectors, electronic magnetic controls and security cameras will scrutinize everyone who attempts to enter, he said.

Between the inner and outer entrances of the Paris fan zone, he said, “we will have what we call a ‘no man’s land,’ to protect against what might happen.”

France will also stage the annual Tour de France bicycle race in July, another event that spans many different locations throughout the country for weeks.

Speaking Sunday on French radio, President François Hollande argued for hosting the games as planned.

“We have invested all the means to succeed, and we must not allow ourselves to be pressured by the threat,” he said.

Martins echoed that sentiment. “If we stop living, if we stop celebrating football, it will be a victory for them, a victory for the terrorists.”

(c) 2016, The Washington Post · James McAuley