The Belgian national team have cancelled Tuesday's scheduled training session out of respect for the victims of the Brussels attacks.Belgium are set to play Portugal in an international friendly at Brussels' King Baudouin Stadium on Tuesday, March 29, but the fixture is now in doubt following suspected terrorist bomb attacks in the nation's capital.Brussels Airport was rocked by a double blast on Tuesday morning while another blast was reported by local media at a Metro station in the city. Several people are feared dead with many more injured.A tweet from the Belgian team's official account, @BelRedDevils, read: "#tousensemble, our thoughts are with the victims. Football is not important today. Training cancelled."Barclays Premier League players including Tottenham defender Jan Vertonghen and Liverpool goalkeeper Simon Mignolet have conveyed messages of alarm and support through Twitter.Seventy-four time Belgium centre-back Vertonghen wrote: "Can't believe I'm reading these things again." while Mignolet tweeted: "#Zaventem" in reference to the location of Brussels Airport. Manchester United winger Adnan Januzaj added: "Horrible to see what is going on in Brussels #Zaventem" Elsewhere, Derdryck Boyata of Celtic wrote: "My thoughts and prayers are with the victims #zaventem"