BRUSSELS (AFP) - Belgian prosecutors on Thursday launched a fresh appeal for help find the suspected surviving attacker in last month's Brussels airport bombings, releasing a video of the escape route taken by the so-called "man in the hat".

Police have been desperately searching for the third suspect ever since he was seen on CCTV next to the two suicide bombers who blew themselves up at the airport in coordinated attacks that also struck a Brussels metro station. A total of 32 people died.

The newly released police video shows the man, wearing a dark hat and a light-coloured jacket, fleeing the airport's departure hall after the bombs went off at 07:58 am on March 22.

CCTV footage shows him continuing his route on foot towards central Brussels where surveillance cameras lose track of him at 09.50am.

Along the way, the fugitive discards his jacket and at one point appears to be on the phone.

"We especially appeal to anyone who might have filmed or think they have photographed the suspect," spokesman Eric Van der Sypt told a press conference to present the video (https://www.youtube.com/watch?v=eso1zW-eRqg).

Investigators are urgently looking for the jacket, described in the statement accompanying the video as light "with a hood which is dark inside".

"Should this jacket be found, this might give invaluable information to the investigators."

Potential witnesses are asked to contact the police using a designated phone number and e-mail address.

Last week, police asked all residents and business owners in the Brussels region who have external surveillance cameras not to delete any footage from March 15 onwards.

Belgian authorities have been criticised for not doing enough to tackle the rise in homegrown extremism, as close links have emerged between the Brussels attackers and those behind the Paris terror assaults in November which left 130 dead.

Both attacks were claimed by the Islamic State in Iraq and Syria (ISIS) group.

A committee of French lawmakers probing the two major terror strikes in Paris last year met in Brussels with Belgian and European counter-terrorism officials on Thursday.

Georges Fenech, who presides over the group, told a press conference that "it is important to make progress on cooperation" between France and Belgium, especially on intelligence sharing and criminal law policy.

The sole surviving suspect in the Paris carnage, Salah Abdeslam, was arrested in Brussels on March 18, just around the corner from his family home, after four months on the run.

He is currently being held in a prison in the northern Belgian city of Bruges, where he is awaiting extradition to France.

He has told investigators he planned to blow himself up outside the Stade de France on Nov 13, but changed his mind.

His lawyer Sven Mary on Thursday said it would be "several weeks" before his client could be transferred to France, as Belgian investigators still had to question him about a police raid at a Brussels apartment on March 15.

That raid triggered a shootout during which several officers were injured and terror suspect Mohamed Belkaid, an Algerian, was shot dead.

Two men fled the scene and prosecutors later said they had found Abdeslam's fingerprints in the apartment.

The 26-year-old French national denies having any prior knowledge of the Brussels attacks, despite having links to at least two of the bombers.

Khalid El Bakraoui, who blew himself up at Maalbeek metro station, rented the flat where the March 15 raid took place.

And one of the two airport bombers, Najim Laachraoui, drove to Hungary with Abdeslam in September.

The ties between the suspects in both attacks have exposed a complex network of cross-border jihadist cells, putting pressure on European security forces to improve cooperation.

Police in several countries have carried out a number of raids and arrests in recent weeks, including some linked to a foiled plot to attack France.

Two suspects in that case, identified as Abderrahmane A. and Rabah M, were remanded in custody in Belgium on Thursday, prosecutors said.

Three suspects held in connection with the Paris attacks, as well as Abdeslam himself, also had their detentions extended, they added.