A man known as Faycal C, the only person arrested and charged with involvement in the Brussels attacks, has been released for lack of evidence.
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 said 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.
