Belgian authorities have raised the terror alert to its highest level in the capital after the fatal shooting of two Swedish people in Brussels which Prime Minister Alexander De Croo suggested was linked to terrorism.

The OCAD anti-terror centre also said the terror alert for the rest of the country had been raised to its second-highest level.

Laura Demullier of the OCAD said the highest priority for authorities had been to get thousands of football fans attending a Belgium-Sweden football match safely out of the the King Baudouin Stadium where the match was abandoned at half-time.

The attacker was still at large and the killings happened three miles from the stadium, where more than 35,000 fans were held for more than two hours.

“The population needs to be actively vigilant and avoid any unnecessary travel,” Ms Demullier said.

Raising the terror level to the top 4 rating means the threat is “extremely serious”. It previously stood at 2, which means the threat was average.

Mr De Croo described those behind the shooting as “cowards”.

Addressing a press conference on Tuesday morning, he said the night was meant to be “a wonderful soccer party” and said the victims had been “cut down by extreme brutality”.

“Terrorism is directed against people everywhere,” he said. “Terrorists will never defeat us and we are fighting it together with our Swedish friends.

“Moments like these are a heavy ordeal but we are never going to let ourselves be intimidated by them.”

Earlier, Mr de Croo had writter on X, formerly known as Twitter: “I have just offered my sincere condolences to @SwedishPM following tonight’s harrowing attack on Swedish citizens in Brussels.

“As close partners the fight against terrorism is a joint one.”

Eric Van Duyse, spokesman for the federal prosecutor’s office, told reporters the investigation was centring on “a possible terrorist motivation for the shooting”.

“During the evening, a claim of responsibility was posted on social media, having been recorded by a person claiming to be the assailant. This person claims to be inspired by Islamic State,” he said.

“The Swedish nationality of the victims was put forward as the probable motive for the act. At this time, no element indicates a possible link with the Israeli-Palestinian situation.”

Mr Van Duyse would not say where the suspect might be or whether more than one person might have been involved. He said the suspected attacker was still at large.

At the football match, he said, “security measures were urgently taken to protect the Swedish supporters”.

“A horrible shooting in Brussels, and the perpetrator is actively being tracked down,” said interior minister Annelies Verlinden, adding that she was joining government talks at the National Crisis Centre.

Media reports aired amateur videos showing a man shooting several times near a station using a large weapon.

A police official said the two victims were Swedes.

Police spokeswoman Ilse Vande Keere said officers arrived at the scene and sealed off the immediate neighbourhood. She declined to elaborate on circumstances of the shooting.

The shooting came at a time of increased vigilance linked to the Israel-Hamas war which has heightened tension in several European nations.

At the same time, the Belgian capital has been the scene of increased violence linked to increasing international drug trafficking.