Belgian police on Tuesday arrested a suspected gunman who shot dead two Swedish football fans in what authorities said was a "terrorist attack".

The arrest, in the Brussels neighbourhood of Schaerbeek, followed an intensive manhunt in the capital for the assailant armed with an automatic rifle.

Police opened fire during the arrest, a spokesman for the Belgian prosecutors' service, Eric Van Duyse, said, without confirming a report by broadcaster RTBF that the suspect was wounded.

Prime Minister Alexander de Croo earlier said the suspect was a man of Tunisian origin who had been living in the country illegally.

"The terrorist attack that happened yesterday was committed with total cowardice, the attacker chose as a target two Swedish football fans," de Croo told a news conference, adding that a third person was seriously wounded.

Sweden expressed its devastation over the shooting -- which occurred just before a Belgium-Sweden football match Monday evening -- and European leaders were quick to offer their solidarity.

Sweden has been at the centre of a bitter row this year with Muslim countries after multiple burnings of the Koran, Islam's holy book.

In a video posted in Arabic on social media, a man identifying himself as the attacker said "he was inspired by the Islamic State" (IS) extremist group, prosecutors said.

The gunman wearing a hi-visibility orange jacket fled on a scooter and Belgian authorities raised the terror alert for Brussels to level four or "very serious" -- the highest -- and level three nationally.

Several Belgian media named the suspect as Abdesalem L, aged 45.

Justice Minister Vincent Van Quickenborn said the asylum seeker was convicted in Tunisia "for common law offences", but was not reported for a terrorist risk.

Prosecutors said the attacker in his video had indicated the Swedish nationality of his victims was a motivation, but there appeared to be no links with the conflict between Israel and Hamas in the Middle East.

"Devastated by the news of two Swedish football supporters murdered in Brussels tonight and a third person being seriously wounded. All my thoughts are with their families and loved ones," Swedish Foreign Minister Tobias Billstrom said.

"Swedish authorities work closely with their Belgian partners to find the murderer," he added on social media.

- Football match abandoned -

As news spread of the killings, the Group F European qualifier match was abandoned at half-time and some 35,000 fans were evacuated from the King Baudouin stadium in Brussels.

Officers provided extra protection for Swedish nationals at the game, escorting Sweden's national players directly to the airport to leave safely, Belgium's football association CEO told the RTBF channel.

"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.

The shooting took place in the city centre's northern districts. Police had been alerted to the incident after 7:00 pm local time (1700 GMT).

In a video shared online by Flemish newspaper Het Laatste Nieuws, the shooter is seen with an automatic weapon on his shoulder, fleeing on a scooter.

Four gunshots can be heard in the video.

A witness who spoke to LN24 channel described his shock during the incident.

"I stood there frozen, I didn't move. I was shocked by what happened, even now I am still in shock. It was a man who came, pushed me, told me to stop running if I wanted to stay alive," said the witness, who gave his name as Sulayman.

The Belgian royal palace said it was "shocked" by the shooting.

- 'Despicable' -

The president of the European Commission, which is based in Brussels, was quick to condemn the attack.

"My thoughts are with the families of the two victims of the despicable attack in Brussels," Ursula von der Leyen posted on social media.

"Together, we stand united against terror," she said.

French President Emmanuel Macron said Europe was "shaken" by an "Islamist" attack in Brussels, while France's interior minister had earlier given instructions to strengthen border controls with Belgium.

Belgium had already been the target of an attack claimed by IS extremists in March 2016, at Brussels' main airport and on the metro system, which killed 32 people.

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