Prosecutors had charged the man identified as Faycal C on Saturday with offences including 'terrorist murder' and had been investigating the theory that he was a third airport attacker who fled when his bomb failed to go off.

His release comes as a new blow to an inquiry already dogged by accusations that Belgium missed a series of leads in cracking down on a militant network linked to the attacks and a similar assault in Paris in November.

Police earlier on Monday released CCTV footage of a third suspect in the March 22 Zaventem airport attack the so-called 'man in the hat' seen with two other men who blew themselves up.

Officials also updated the death toll from the bombings at the airport and at Maalbeek metro station to 35 the worst terror attacks in Belgium's history after four more people had died in hospital.

Mourners were set to hold an Easter Monday church service in memory of the victims.

The Belgian federal prosecutor's office said in a statement that 'the indications 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'.

A source close to the inquiry said: "Investigators have established that he was not the 'man in the hat'."

Belgian media had identified the man as Faycal Cheffou who claimed to be a freelance journalist.

With the manhunt still underway police released video of a man in a hat and white jacket pushing a trolley with a large bag through the departure hall next to suicide bombers Ibrahim El Bakraoui and Najim Laachraoui.

As Belgium struggles to come to terms with the tragedy recriminations continue over whether the authorities could have prevented it as the links to the Paris attacks in which 130 people were killed become clearer by the day.

Bomb-maker Laachraoui's DNA was found on some of the explosives used in Paris.

Metro bomber Khalid El Bakraoui Ibrahim's brother is meanwhile believed to have rented a property linked to Paris prime suspect Salah Abdeslam who was arrested in Brussels on March 18 just yards from his family home after four months on the run.

And Turkey accused Belgium last week of ignoring a clear and present danger after revealing it had deported Ibrahim El Bakraoui as a 'terrorist fighter' last year after arresting him near the Syrian border.

Two Belgian ministers offered to resign after the Turkish link emerged.

Prosecutors earlier said three men arrested in raids in Belgium at the weekend had been charged with 'participation in the activities of a terrorist group' but that no direct link had been established with the Brussels attacks.

The men - identified as Yassine A. Mohamed B. and Aboubaker O. - were held during 13 raids in Brussels and the towns of Mechelen and Duffel. A fourth person arrested at the same time was released.

In the latest piece in the puzzle of the militant cross-border networks police arrested a 32 year old French national in Rotterdam on Sunday on suspicion of planning a terror attack Dutch prosecutors said following a raid carried out at the request of French authorities.

The man is thought to have been planning an attack in France in the name of the Islamic State group along with Reda Kriket who was detained near Paris on Thursday a French police source said.

Belgian prosecutors at the weekend also charged two men with involvement in the Kriket plot including one shot in the leg after a dramatic stand-off at a tram stop in Brussels on Friday.

An Algerian held in Italy as part of a probe into fake ID documents used by the Paris and Brussels attackers is still being interrogated but refused to answer questions a judicial source said.

The tensions in Belgium were underscored on Sunday when police used water cannon to disperse far-right football hooligans chanting anti-immigrant slogans disrupted the makeshift memorial to the victims in central Brussels.

Belgium's government crisis centre said Monday that 31 victims were confirmed dead at the scene of the airport and metro attacks while four had since died in hospital.

'Medical teams did all possible' tweeted Belgian Health Minister Maggie De Block adding: 'Courage to all the families'.

Twenty eight victims had been formally identified she said. The US State Department on Sunday confirmed the death of two more Americans bringing the total to four.

Brussels Airport said it would carry out a test run on Tuesday to see if the repair work in the wrecked departure hall was satisfactory but it could not give a firm date for resuming services.