UEFA cannot rule out the prospect that games at this summer's European Championship could be played behind closed doors if there are sufficient concerns over terrorism, according to its executive committee vice-president Giancarlo Abete.
Authorities ruled out a cancellation or relocation of Euro 2016 after November's terror attacks in Paris, and France's Interior Minister, Bernard Cazeneuve, re-emphasised the importance of high security at the tournament in light of Tuesday's deadly explosions in neighbouring Belgium.
However, UEFA's Abete, who also served as Italian FA (FIGC) president between 2007 and 2014, said they may have to consider the possibility that games at the tournament could be played without supporters if "significant risks emerge."
"Security is the primary problem for all of us," he told Radio 24. "The sporting event is only secondary to the issue of people's security. For every sporting event, there is somebody responsible for public order who is above any other person responsible for the organisation of the sporting event.
"The last two World Cups, first in South Africa and then in Brazil, were both characterised by the risk of incidents and social tension, for different reasons. It is something that unfortunately the world of sport has to live with.
"We need to keep our heads held high and keep faith in the values we trust. We need professionalism and sensitivity to take certain decisions, by staging as many events as possible and postponing or cancelling them in the moment in which significant risks emerge.
"There is always a risk of having to play behind closed doors because we're talking about a competition that has got to take place. You cannot postpone matches to a later date because it's a tournament that relies on results for it to proceed.
"It seems like the priorities today are different. We're talking about events that have already had a negative impact on the tournament -- there's a greater perception of risk and less enthusiasm to participate with positive spirits -- but we're still talking about a tournament scheduled for June, and we're talking about an emergency taking place right now.
"Italy play against Belgium at the European Championship and we have all got to carry on as normal. As sports officials, we need to continue working with faith and concern, understanding that these are battles you only win by maintaining a positive spirit."
UEFA later said in a statement that there are no existing plans to play games without supporters but suggested it was a possibility in "crisis situations."
The statement read: "We are confident that all security measures will be in place for a safe and festive Euro and therefore there are no plans to play matches behind closed doors.
"However, we are nevertheless working on contingency plans and on multiple scenarios around crisis situations since we take the security of all participants (players, fans, etc) very seriously."
French secretary of state for sport Thierry Braillard underlined that there is still no prospect of Euro 2016, which begins on June 10, being cancelled following this week's incidents in Brussels.
Asked if the competition might be postponed if there were further attacks in France, Braillard told L'Equipe: "In moments like these, we shouldn't add fear on top of fear. I don't respond to 'ifs' and I don't ask questions that don't arise... the Euros will not be postponed or cancelled.
"We've been repeating it for several months -- the terrorist threat was incorporated into our thinking from the start. To cancel or postpone the European football Championship would be to prove these cowards right."
French Prime Minister Manuel Valls has also said that Euro 2016 should not be postponed.
"No, that would be a defeat -- it would be to give a victory to the terrorists," he told Europe 1 radio station. "The big sporting events, the big cultural events, the big popular events are vital to show that we are a free people, on our feet, that we are not afraid.
"So, yes, Euro 2016, like the Tour de France and other big events, will take place."
He reaffirmed that every step possible would be taken to try to guarantee that the tournament will be played out in the best conditions possible.
"All the resources will be deployed -- public, discreet, intelligence -- to ensure safety, but there is not zero risk when faced with people who are determined to die," he said. "Life is the best of responses in the face of ideology of death."
Wales boss Chris Coleman told BBC Sport that "everybody wants" the tournament to go ahead as planned.
Referring to the attackers, he said: "I think these people would have us stay in our houses, locked up 24 hours a day if we let them have their way. That shouldn't happen.
"If somebody's hell bent on walking into a crowded area and they want to blow themselves up or whatever, there's only so much security can do.
"There's always going to be a doubt in everybody's mind. You're hoping and praying that everything's going to be OK.
"We've all got to go there and try to enjoy the tournament, try to entertain everybody that's going there as best we can."
ESPN FC correspondents Ben Gladwell and Mark Rodden contributed to this report.