Worried, but relieved, spectators at the Belgium-Sweden Euro 2024 match left the Brussels stadium shortly before midnight after being held there for two-and-a-half hours following the killing of two Swedes in a nearby attack, with the gunman still at large.

"I was stressed, I wondered how we were going to get back, because we came by metro," Manon Antoine, 21, told AFP, accompanied by her brother.

The Swedish supporters were the last to leave the King Baudouin Stadium, where some 35,000 fans of the two teams had turned out for the Euro 2024 qualifier.

Manu Leroy, CEO of the Belgian football association, said police had escorted the Swedish fans and players to "go straight to the airport and leave" because the perpetrator, who was said to be inspired by the Islamic State group, was still on the run and being sought by police early Tuesday.

According to investigators, the Swedish nationality of the victims was a "probable motivation" of the attacker, according to his video claim.

Several Belgian media outlets said the two individuals killed were wearing football shirts belonging to the Swedish national team.

The area around the stadium, located about five kilometres (three miles) from the scene of the attack, was being monitored by police, and traffic past the ground had been halted.

- 'The safest place' -

About 10 minutes before kickoff, match organisers learned that "something serious had happened", Leroy said on RTBF.

"At first it was decided that the match should go ahead because the stadium was the safest place for the fans, especially the Swedish fans so that they would be safe," he said.

But at halftime, the match was halted with the score at 1-1 and did not restart.

UEFA said the decision to abandon the game was taken after consultation with both teams and the Belgian authorities.

"I am terribly sad. We agreed 100 percent not to play the second half because of the conditions and out of respect for the victims and their families," said Sweden coach Janne Andersson, quoted by the Swedish news agency TT.

Held inside the stadium as a security precaution, the fans braved the cold and the anxiety by singing songs in honour of Sweden and chanting "All together, all together!".

"I think that we all tried to keep our spirits up. We also sang little songs for the Sweden supporters because it is especially for them that it is a very sad evening," said football fan Jacques Decoq outside the stadium.

"We tried to stay warm with a little bit of atmosphere."

Applause also punctuated the long wait.

Finally, shortly before midnight, Red Devils fans began to leave the stadium, the authorities having chosen to evacuate the Belgian supporters stand by stand to avoid crowds.

"Everyone remained very calm, the supporters started singing, there was an atmosphere, even if we were a little worried," said Karen, who came from Limburg with her family.

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