Shortly after the game was abandoned and the crowd was advised to remain in the stadium. Mobile phone networks quickly became overloaded, Van Overstraeten said, as people sought details from outside.

Less than 5 km (3 miles) away, two Swedish nationals had been shot dead in the street. The Federal Belgium prosecutor said the suspected assailant, who was still on the loose, had claimed in a video on social media that he was a fighter for Allah.

Van Overstraeten said the crowd chanted 'all together' and 'Sweden' as it waited.

The match was abandoned at half-time with the score level at 1-1. Olaf Gill, a European Commission spokesperson, said he read the news and left the stadium still wearing his Sweden jersey.

"Helicopters, armed police everywhere. Police advised: 'Don’t show your colours'. Zipped up jacket," Gill tweeted. "Sad night in Brussels."

As the cold set in, those in the crowd who remained sat quietly, waiting for updates on an evacuation.

"We don't have many details," Van Overstraeten said. "Every 10 to 15 minutes the speaker thanks people for their patience and urges calm."

Dozens of Swedish fans were still inside the stadium at 1.30am (12.30am BST) awaiting a police escort out of the stadium, one fan said.