UEFA says there are no plans to hold any matches at Euro 2016 behind closed doors following Tuesday's terrorist attacks in Brussels.
At least 34 people were killed following explosions at Zaventem airport and the Maalbeek metro station in the Belgian capital.
UEFA vice-president Giancarlo Abete told Italian radio on Tuesday evening: "We can't exclude the possibility of playing behind closed doors, as we cannot exclude terrorism."
European football's governing body has always maintained playing games with no fans present was one of several security options they would consider to protect the public at this summer's tournament in France - but have moved quickly to reassure fans that this is not being considered at present.
A UEFA 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."
Jacques Lambert, head of Euro 2016's organising committee told French radio that it would be "absurd" to play games behind closed doors.
"We must demonstrate cool, sensible and responsible organisation of Euro 2016," he told Europe 1.
"It would be absurd to play matches at Euro 2016 in empty stadiums.
"The fan zones will be subject to the same security measures as the stadiums."
Belgium's national squad cancelled training sessions on both Tuesday and Wednesday - and their friendly against Portugal will now be played in Leiria rather than in Brussels as originally planned.