Belgian media gave his name as Faycal Cheffou and said he was suspected of being the mystery third man seen in CCTV footage of the bombers.
Tuesday’s attacks on the airport and the city’s metro system killed 35 people and injured more than 300.
The attacks were claimed by the Islamic State (IS) militant group.
Police have blocked off a Brussels square, Place de la Bourse, which saw clashes between police and nationalist protesters on Sunday. Officers told the BBC there was a “security issue”.
People were allowed to stay in the square, where mourners have placed candles, wreaths and messages for victims of the bomb attacks.
Of the 35 victims, seven have still to be identified, the country’s crisis centre said on Monday (in French).
At least 12 of the victims are foreign nationals from the US, the Netherlands, Sweden, Germany, France, the UK, Italy and China, it said earlier.
The death toll does not include three attackers, two of whom blew themselves up at the airport and one in the metro.
EU institutions based in Brussels will reopen on Tuesday, following the Easter break, “with important additional security measures in place”, European Commission Vice-President Kristalina Georgieva said in a tweet.
Belgium terror arrests
A man referred to officially as Facyal C was released on 28 March after being arrested on 24 March in Brussels and charged with “participation in the activities of a terrorist group, terrorist murders and attempted terrorist murders”.
Others detained on suspicion of terrorist activity include
- Salah Abdeslam – arrested on 18 March in the Molenbeek district of Brussels. Key suspect in the Paris attacks last November. Charged with “terrorist murder”
- ‘Amine Choukri’ – arrested on 18 March with Abdeslam, real name not yet known. Also used the alias Monir Ahmed Alaaj. Documented by German police near Ulm in a car with Abdeslam last October. Charged with “terrorist murder” over the Paris attacks
- Rabah N – arrested on 25 March and charged with participating in terrorist activities in relation to a foiled plot to attack Paris
- Abderamane A – shot in the leg and arrested on 25 March at a tram stop in the Schaerbeek area of Brussels. Charged in relation to the foiled plot to attack Paris. Jailed for seven years in France in 2005 and banned from entering France for life aiding in the assassination of Afghan commander Ahmed Shah Massoud in 2001.
- Aboubakar A – arrested on 24 March in a car in Brussels, charged with participating in terrorist activities
- Yassine A, Mohamed B and Aboubaker O – arrested during raids on 27 March and charged with belonging to a terrorist group
In a statement, the Belgian federal prosecutor’s office said: “The clues that led to the arrest of Faycal C were not substantiated by the ongoing inquiry.
“As a result, the subject has been released by the examining magistrate.”
He had been charged only two days before with “taking part in a terrorist group, terrorist murder and attempted terrorist murder”.
Belgian public TV and Le Soir daily identified the freed man as Mr Cheffou, a freelance journalist.
CCTV footage released by Belgian police on Monday shows the two airport bombers alongside a third man, who is wearing light-coloured clothing and a dark hat. Each is pushing a loaded luggage trolley.
Twin blasts struck the main terminal of Zaventem Airport, in the north-east of the city. A third, even bigger, bomb was abandoned, prosecutors said at the time. It exploded after the security forces had secured the scene and nobody was hurt, they added.
The man in the hat is believed to have fled the scene.
Tuesday’s other attack targeted the Maelbeek metro station in the city centre, close to several EU institutions.
Brussels was the second large-scale attack on an EU capital city claimed by IS, after gunmen and bombers killed 130 people in Paris on 13 November.
IS, an extreme Sunni Muslim group known for its ruthless tactics, has seized large tracts of territory in Syria and Iraq in recent years, attracting hundreds of young Europeans to its ranks, many of them Belgians.
[Source:- BBC News]