Belgian authorities say they foiled a terror attack when troops shot and killed a suspected suicide bomber at Brussels Central Station.

Counter-terrorism police are investigating the identity of shot dead by troops guarding a Brussels railway station after he set off explosives that failed to injure anyone.

Local media reported the man wearing what appeared to be a “explosives vest”.

There were no other casualties.

Federal prosecutor Eric Van der Sypt confirmed “this incident is considered as a terrorist attack”.

Witnesses said there were two loud explosions and a fire at the station.

Belgian prosecutor’s spokeswoman Ine Van Wymersch said medics were unable to attend to the man for several hours out of fear he could be carrying explosives and his death was only confirmed once a bomb squad had finished its work.

Mr Van der Sypt earlier said soldiers “neutralised” the man immediately after a small explosion at the station.

Nicolas Van Herrewegen, a station employee, told public broadcaster RTBF he saw a man shouting in a lower level of the busy station, which serves lines running under the city centre.

He appeared to yell “Allahu Akbar” in Arabic and detonate something on a luggage trolley. People standing within three metres of the trolley were unhurt, Mr Herrewegen said.

Belgium’s Crisis Centre, which monitors security threats in the country, says that based on initial information, it doesn’t see a need to raise the terror threat in the country to the highest level.

Photos posted on social media showed a small fire in the station, which was evacuated along with the main Brussels square. 

The Belgian capital, home to the headquarters of NATO and the European Union, has been on high alert since a Brussels-based Islamic State cell launched an attack that killed 130 people in Paris in November 2015. 

Associates of those attackers, four months later, killed 32 people in their home city, including with bombs loaded on trolleys at Brussels Airport.

Combat troops have been a fixture at transport hubs and in the main public areas ever since the Paris attacks.

Prime Minister Charles Michel urged citizens via Twitter to follow instructions from the authorities.

The station and adjacent historic downtown area, including the baroque Grand Place city square were packed with tourists and locals on a hot summer evening.

Het Laatste Nieuws newspaper reported witnesses saying a man shouted “Allahu Akbar” in Arabic before a small explosion.

Soldiers ran toward the spot, saw wires protruding from the man’s clothes, and shot him. That account could not be independently confirmed.

However, stationmaster Jean-Michel Michel was quoted by DH newspaper saying: “We heard the explosion. My colleague thought it was a bomb. The explosion was on the mezzanine level.

The man went down to platforms three and four. He said ‘Allahu Akbar’… I would put him at about 35 years old.”

– with AAP