Turkey said on Wednesday it had detained and then deported one of the two suspected suicide bombers at Brussels airport, suggesting Belgian authorities ignored a warning that he was a "foreign terrorist fighter".

President Recep Tayyip Erdogan said Turkish authorities detained Brahim el-Bakraoui in June last year in Gaziantep, close to the Syrian border, and then deported him to the Netherlands in July at his request.

"We reported the deportation to the Belgian Embassy in Ankara on July 14, 2015, but he was later set free,"  Erdogan told reporters in Ankara.

"Despite our warnings that this person was a foreign terrorist fighter, the Belgian authorities could not identify a link to terrorism." 

Erdogan did not specify how Bakraoui had been transferred from the Netherlands to Belgium, where 31 people died and 270 people were wounded in the bomb attacks at the capital's airport and on a metro train on Tuesday morning.

Brussels victims came from around the world

Belgium has not yet replied to Erdogan's claims.

The manhunt intensified on Wednesday for a suspect seen with Bakraoui and another alleged suicide bomber shortly before they struck Brussels' airport.

Bakraoui, pictured in the middle of a surveillance photo at the airport, was identified using finger print records, Belgian Federal Prosecutor Frederic Van Leeuw said on Wednesday.

Bakraoui's brother, Khalid, blew himself up on a metro carriage at Maelbeek station.

The second airport suicide bomber, on the left of the picture, has been identified as Najim Laachraoui.

The third, who left the airport before the explosions, is also not yet identified and remains on the run. The explosives he wheeled in failed to detonate until most people in the airport had fled, Van Leeuw said.

#BrusselsAttacks: Grief, Islam and double standards

The prosecutor also confirmed that police had carried out raids following Tuesday's attacks, including at an address associated with the suspects after a tip-off by a taxi driver who drove the attackers to the airport.

During a house search in the Brussels neighbourhood of Schaerbeek, investigators found 15 kilograms of explosives, detonators, and chemical products, Van Leeuw said.

Police also found a computer in a rubbish container in the street that included a note by Bakraoui, the airport bomber, in which he said he felt increasingly unsafe and feared landing in prison.

"Always on the run, not knowing what to do any more, being looked for everywhere, not being safe any longer," the prosecutor quoted the message as saying.

Van Leeuw said one person detained in one of the raids remained in custody on Wednesday and was being questioned.

The prosecutor spoke shortly after crowds of mourners gathered outside Maelbeek station and observed a minute of silence.

The Islamic State of Iraq and the Levant group (ISIL, also known as ISIS) claimed responsibility for the attacks, which struck the heart of European officialdom where NATO headquarters is based, along with the European Union, and European Commission.  

The interior ministry raised the country's terrorism alert to the highest level after the blasts.   

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Source: Al Jazeera and agencies