Brussels bombers on CCTV
Brussels bombers on CCTVPublic Domain/Wikicommons

Najim Laachraoui, one of the Brussels airport suicide bombers, has been identified by several Frenchmen held hostage by Islamic State (ISIS) in Syria as one of their prison guards, sources close to the investigation said.

According to one of the sources, four French journalists kidnapped in Syria in 2013 and 2014 had identified a guard known as "Abou Idriss."

One of these journalists, Nicolas Henin, "formally identified" Abou Idriss as Najim Laachraoui, said his lawyer Marie-Laure Ingouf, confirming reports in French newspapers.

Laachraoui was one of the two suicide bombers at the airport on March 22 in coordinated attacks that also struck a metro station in the city, murdering 32 people overall.

It was previously reported that Laachraoui worked as a janitor at the European Parliament for one month in 2009 and one month in 2010. He also worked at the Zaventem Airport - the site of the attack. 

Traces of Laachraoui's DNA have been found at a Brussels apartment where the suicide belts for the Brussels attacks were made.

He is also suspected of being the bomb-maker for last November's Paris attacks that left 130 people dead.

Belgian prosecutors believe Laachraoui went to Syria in February of 2013 where he joined ISIS, which claimed responsibility for the Brussels attacks.

He resurfaced last September, two months before the Paris carnage, when he was stopped by police on the Austria-Hungary border, according to AFP.

Laachraoui was reportedly using the false identity of Soufiane Kayal and was travelling with Salah Abdeslam, the sole surviving Paris attacks suspect who was recently apprehended.