Several Belgian media outlets said the two individuals killed were wearing the jersey of the Sweden national team.
Belgium's Euro 2024 qualifier against Sweden was abandoned at half-time and fans were kept in the stadium for security reasons after two Swedes were shot dead in an attack in Brussels on Monday.
Spectators at the King Baudouin stadium in the Belgian capital were told to remain inside the ground following an announcement that the players would not return for the second half.
"Following a suspected terrorist attack in Brussels this evening, it has been decided after consultation with the two teams and the local police authorities, that the UEFA EURO 2024
Sweden's football association said Belgian police had told supporters "to stay in the arena for security reasons".
Two Swedish nationals were shot dead by a suspect who remains at large, in an attack the Belgian prime minister described as "terrorism".
Several Belgian media outlets said the two individuals killed were wearing the jersey of the Sweden national team.