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."
"I wanted to play in Brussels, at home, because I am against fear," said Belgium coach Marc Wilmots.
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"I wanted to play here to show them (the terrorists) that despite the terrible events, which shook the country, life goes on for the majority of people."
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.
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.
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.
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."
"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."
"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.