UEFA will consider playing Euro 2016 without supporters if the terrorism threat rises in the next three months, the governing body's executive committee vice-president has said.
Giancarlo Abete, vice-president since 2011, told Italian radio that more extreme measures may have to be taken for the tournament in France following Tuesday's terror attacks in Belgium.
The former head of the Italian FA told Radio24: "Euro 2016 is the kind of event that we can't delay or postpone.
"We can't exclude the possibility of playing behind closed doors, as we cannot exclude terrorism. If we talked about potentially cancellable games, such as a friendly or a competitive match, they could be moved to another date.
"Obviously this would not be the case. But we are talking about games which are staged for June whereas, today, we are going through a very urgent emergency."
At least 34 people were killed in Brussels following explosions at Zavantem Airport and Maalbeek metro station.
Belgium's national squad cancelled their training session yesterday and their friendly against Portugal in Brussels next week is in serious doubt.
FIFA has released a statement reaffirming its commitment to guaranteeing a "safe and secure" Euro 2016 in France this summer.