Updated 1.55pm

Belgian police on Tuesday shot and fatally wounded an alleged Islamist accused of gunning down two Swedish football fans visiting Brussels, as Sweden faces what its premier said was an unprecedented security threat.

The attack was launched in central Brussels late on Monday, when a gunman opened fire on Swedes ahead of a football match, killing two of them and wounding a third, before leading police on an overnight manhunt.

The suspect was cornered and fatally wounded early on Tuesday, when Belgian police moved to detain him in a cafe.

Interior Minister Annelies Verlinden said in a social media post that the dead man had been positively identified as the perpetrator of the murders.

"During the operation shots were fired and the suspect was gunned down," the federal prosecutor's office said.

Paramedics attempted to revive him at the scene before he was transferred to hospital, where his death was confirmed.

The incident triggered dismay in Brussels, where the Belgium-Sweden international match was called off at half-time, and also in the dead fans' homeland.

Swedish Prime Minister Ulf Kristersson said: "Sweden has in modern times never been under as big a threat as now."

In recent months, Swedish authorities have issued permits for several protests at which copies of the Koran, Islam's holy book, were burned -- triggering angry diplomatic protests from several Muslim countries and a wave of protests.

"Every indication is that this is a terror attack, targeting Sweden and Swedish citizens, just because they are Swedes," Kristersson said, adding he felt an "unfathomable sadness".

Total cowardice

In August, Sweden's intelligence service, SAPO, raised its threat level to four on a scale of five after the Koran burnings. 

"It was risks like this that were the reason SAPO this summer raised the threat level," Kristersson said.

Belgian Prime Minister Alexander de Croo said the suspect was of Tunisian origin and had been living in the country illegally. 

In a social media post after the killings, the gunman had boasted of being inspired by the Islamic State extremist group.

"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.

He said a fourth person -- a taxi driver -- had been seriously wounded.

"Terrorism strikes indiscriminately," he said. "It aims to sow fear, mistrust and division in our free societies. Terrorists must know that they will never achieve their goals. 

The gunman, wearing a hi-visibility orange jacket, fled on a scooter and Belgian authorities raised the terror alert to level four -- the highest -- in Brussels and to level three nationally.

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

Prosecutors said the attacker in his video had indicated that the Swedish nationality of his victims was a motivation.

There appeared to be no links with the conflict between Israel and Hamas in the Middle East.

Football match abandoned

As news spread of the killings, the Group F European qualifier match between Belgium and Sweden was abandoned at half-time. 

Some 35,000 fans were evacuated from the King Baudouin stadium in Brussels.  

Officers provided extra protection for Swedish nationals at the game and escorted Sweden's 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.

Brussels' Swedish Lutheran church was closed after the attacks on police advice. 

It was able to counsel some shocked and frightened compatriots by telephone, Pastor Fredrik Ollila told AFP.

The shooting took place in the north of the city. 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.

Belgium was the target of an attack claimed by IS extremists in March 2016, when suicide bombers targeted Brussels' main airport and the metro system, killing 35 people.