Belgian troops shot a suspected suicide bomber in Brussels Central Station on Tuesday but there were no other casualties and the situation was brought under control after people were evacuated, Reuters reported.
A Reuters correspondent at the scene an hour after the incident - in which police said the man set off a small explosion - said the area was quiet, with police manning a cordon and a few bystanders calmly watching security forces.
Amid conflicting accounts of what happened, it was still unclear if the man had died. Paul de Vries, a Dutchman working in Brussels, told Reuters he saw police taking away a prisoner.
Nicolas Van Herrewegen, a station employee, told public broadcaster RTBF that he saw a man shouting in a lower level of the 1930s station, which serves lines running under the city center. He then appeared to yell "Allahu Akbar" in Arabic and to detonate something on a luggage trolley. People standing within three meters of the trolley were unhurt, Herrewegen said.
Authorities were investigating whether it was a terrorist incident, a spokesman for the national Crisis Centre said. The national alert level was maintained at its second highest level.
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. A series of further attacks in neighboring France and Germany in the past year, as well as recent bloodshed in London and Manchester, have added to anxiety.
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 3 and 4. He said 'Allahu Akbar'...
"I would put him at about 35 years old."
The station and adjacent historic downtown area, including the baroque Grand Place city square, had been packed with tourists and locals on a hot summer evening before they were evacuated.
The police spokesman said: "There was an incident at Central Station. There was an explosion around a person. That person was neutralized by the soldiers that were on the scene.
"At the moment, the police are in numbers at the station and everything is under control."
Prime Minister Charles Michel and the interior minister were in the national crisis center monitoring developments.