Belgian authorities are raiding the neighbourhood of the bombmaker thought to be behind November's Paris attacks as experts say he may have designed the explosives that killed at least 31 people today in Brussels.

Najim Laachraoui, 24, is also suspected of being responsible for the bombs used in the Paris massacre after it was revealed his DNA was found on suicide belts used in the Bataclan Theatre and the Stade de France.

Laachraoui reportedly travelled to Syria in February 2013 and was stopped by guards at the Austria-Hungary border on September 9 last year while driving a rented Mercedes he shared with Salah Abdesalam, according to the Belgian Federal Prosecutor.

Hunted: Police are hunting Najim Laachraoui, 25, who is wanted in connection to both the Paris and Brussels attacks

Suspects: Belgian Police released this CCTV image of the suspected bombers behind the airport attack

He is thought to be the Brussels ISIS cell's 'bomb maker' after his DNA was found on suicide belts found in the Bataclan Theatre and Stade de France in November

The pair were also travelling with Mohamed Belkaid, 35, the man shot and killed during the raid to capture Abdelslam on Friday.

It is thought Laachraoui was not stopped as he was using a drivers licence under a different name and traveled to Budapest twice in September 2015.

On this instance, the three men had posed as tourists heading to Vienna on holiday and did not raise suspicions when they were stopped by police.

Laachraoui was also captured on CCTV with Belkaid four days after the attacks during a money transfer in a Western Union bank in the Brussels area.

'The investigation showed that Soufiane Kayal can be identified as Najim Laachraoui, born on May 18, 1991 and who travelled to Syria in February 2013,' prosecutors said in a statement in Brussels.

It is also using this alias that authorities have said he was in contact via phone with Paris attacks ringleader Abdelhamid Abaaoud, and gave him guidance in the lead-up to the November attacks.

He has been identified as using the alias Soufiane Kayal - the name he used to rent the safe house used by the Paris bombers to plan the Paris attack, where his DNA has also been found as well as in their hideout in Schaerbeek.

At the house on Rue Henri Berge, investigators found traces of TATP - a signature explosive of ISIS in Europe, and was found in the suicide vests used by the Paris attackers.

It comes as Belgian federal prosecutors say a house search in the Brussels neighborhood of Schaerbeek has 'led to the discovery of an explosive device containing among other things nails.'

Investigators also found chemical products and an Islamic State flag.

A Belgian prosecutor says police raids are happening around the country after two men 'probably' staged suicide bombings at the Brussels airport and a third fled.

Prosecutor Frederic Van Leeuw said Tuesday that the third suspect - on the right of the photo wearing a thick white sweater - is actively being sought by police.

The 'masterbomber' Najim is believed to have studied electro-mechanical engineering at a Catholic high school named as the Institute de la Sainte-Famille d'Helmet by in an investigation by The New York Times.

Authorities say it's not possible at this stage to establish any links between the attacks Tuesday in Brussels and those in Paris on November 13 that left 130 people dead.

Mr Pantucci, the Director of International Security Studies at the Royal United Services Institute, said information surrounding the 'mystery bomb maker' Najim Laachraoui is still very sketchy.

He said: 'We don't know much about him at this point. This individual is being identified as a bomb maker but we have concerns whether that is 100 per cent true or if he's one of a number of bomb makers.

'This terrorist group in Brussels had multiple, viable explosive devices. It suggests they were dealing with someone with substantial experience.

'That could be the same person responsible for the bomb devices in the Paris attacks but it could be someone else, part of a larger cell.

'Given the location and the nature and the use of explosives and guns the thought process goes down the page of assuming it's linked to the organised network around Abdeslam.

'We can't be sure but it would be surprising if it wasn't the same group.'

Foreign Minister Didier Reynders said on Sunday that Salah Abdeslam, who was arrested on Friday when was caught was 500 metres from his childhood home, had claimed that 'he was ready to restart something from Brussels, and it's maybe the reality,'

Reynders gave credence to the suspect's claim because 'we found a lot of weapons, heavy weapons in the first investigations, and we have seen a new network of people around him in Brussels.'

Killed and Captured: Mohamed Belkaid, 35 (left) was killed during the raid that ended in the capture of failed suicide bomber Salah Abdeslam (right). Both were travelling in a car crossing the Austrian-Hungrarian border with suspected bomb maker Najim Laachraoui in September

He also said that the authorities are searching for up to 30 people in Belgium and France in connection with the Paris attacks.

A friend of Abdelhamid Abaaoud, who masterminded the November 2015 Paris attacks, told police that the jihadi claimed he was among 90 terrorists who smuggled themselves across the Mediterranean with migrants and refugees.

Abdeslam relied on two friends to drive him back to Brussels after his brother Brahim blew himself up at a Paris cafe.

Others drove him around Molenbeek and its environs between safe houses.

Arrested: Salah Abdeslam was arrested on Friday - his lawyer says that he may become an informer

Authorities are also searching for Mohamed Abrini, 31, who was filmed with Abdeslam at a petrol station on a highway to Paris two days before the Paris attacks and has been missing since November 12.

It has been reported that Abrini's brother Souleyman, 20, died in Syria in 2014 while fighting for a militia led by Abdelhamid Abaaoud - the 'mastermind' of the Paris attacks.

Police, who were eventually able to move in to seize Abdeslam at a house in the rundown North African neighbourhood of Molenbeek four days ago, have charged a man and a women whom they suspect of being part of a family who harboured the fugitive.

It is understood that intelligence services located the fugitive's hideout after listening in on phone conversations at the funeral of his brother, Brahim Abdeslam, who blew himself up in the Paris attacks.

One mourner is thought to have let slip vital information which allowed police to close the net around Abdeslam in Molenbeek.

They finally snared him after they noticed a large number of pizzas being delivered to a flat they had under surveillance – too many for the number of people who should have been in the apartment.

Aftermath: The explosion that ripped through the terminal at 8am local time killed at least 14 people

Terror: The second explosion hit a train stopped at Maelbeek metro station, near to Brussel's EU offices

He was interviewed three times on Saturday, the day after his capture - once by prosecutors and twice by an investigating judge - and 'wasn't in great shape' because he had been shot in the leg by police during his capture, Mr Van Leeuw said.

Abdeslam has a court hearing on Wednesday. France has requested his extradition but Abdeslam's lawyer says his client will fight the request.

Federal police in Belgium have issued a wanted notice for a suspect in the Brussels airport bombing that they are still trying to identify.

A man wearing a thick light-colored jacket with a black hat and glasses is suspected of committing an attack at Zaventem airport on Tuesday morning.