But Europe’s governing body and the French government insisted that Euro 2016 will go ahead and there will be no games behind closed doors.
Belgium, the world’s top ranked team, had been due to play Portugal in Brussels next Tuesday.
But a day after the attacks on Brussels airport and the city metro in which 31 people died, the Belgian federation said the match had been called off for “security reasons.”
Portugal’s federation later announced that the two countries had agreed to play the match the same day in the Portuguese city of Leiria instead.
The Islamic State assaults on Paris and Brussels over the past four months have increased the security spotlight on the 24-nation European Championships due to start in Paris on June 10.
One of the deadly suicide attacks in Paris on November 13 was against the Stade de France and security will again be heightened when France play Russia there on Tuesday, authorities said. France’s games against the Netherlands in Amsterdam on Friday has also been confirmed.
UEFA and France say they are determined that Euro 2016 should go ahead.
French Prime Minister Manuel Valls said not holding the tournament would be “a victory for terrorists.”
UEFA also expressed confidence in the money-spinning event but added that it had planning for “crisis situations.”
“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,” UEFA spokesman Pedro Pinto told AFP.
“Nevertheless we are working on contingency plans and on multiple scenarios around crisis situations since we take the security of all participants very seriously,” he added without giving details.
His comments came after Italian UEFA vice president Giancarlo Abete said Europe’s governing body could not rule out holding Euro 2016 games without fans but that it was not yet being considered.
“From a technical point of view, the risk of ‘closed doors’ can always exist because we are talking about a competition where the matches must take place,” Abete told Radio 24.
But he told Gazzetta dello Sport newspaper that “today there is no structural situation that means we are thinking of disputing the Euro behind closed doors.”
Designated fan-zones in the 10 host cities which could attract hundreds of thousands of supporters from across Europe have caused particular concern.
But French Football Federation president Noel Le Graet told AFP it would be a “dramatic” move to call off Euro 2016 because of the risk of attacks.
“I am not worried,” Le Graet told AFP in an interview.
“Even though we can see that attacks are unpredictable, I am sure that everything will go well.
“Our role is to reassure because there are people who may be scared, we cannot control that.
“But everything has been laid on so that the matches go ahead in good conditions. Everything is being done, with an enormous mobilisation of a security system in the interests of the population.”
Le Graet said extra security had already been ordered for the France-Russia game on Tuesday. Suicide bombers failed to get into the stadium on November 13 and set off their explosives outside.
“Despite what happened on November 13, we can consider that the stadium was protected,” said Le Graet. “The new measures protect it even more. Do we need to do more. I don’t think so. There is a level of security that seems sufficient to me.”