Sven Mary, lawyer of key suspect in the Paris terror attacks Salah Abdeslam | Kenzo Tribouillard/AFP via Getty Images Lawyer: Paris attack suspect more radical since arrest ‘He’s got a beard, he’s become a true fundamentalist whereas before he was a kid wearing Nike trainers.’

The main suspect behind the Paris attacks, Salah Abdeslam, has become more radicalized since his imprisonment for his alleged role in last year's assault that left 130 people dead, according to his former lawyer quoted in a report by AFP reports.

"He's got a beard, he's become a true fundamentalist whereas before he was a kid wearing Nike trainers," Belgian lawyer Sven Mary said in an interview with Dutch newspaper De Volkskrant that was published on Saturday.

Belgian-born and French national Abdeslam, is thought to be the only survivor of the group of assailants behind the November 13, 2015 attacks in Paris. ISIL claim responsibility for the assault that Belgian authorities claim had been orchestrated by the militant group's top leaders, based in Iraq and Syria.

Abdeslam, a 27-year-old Belgian resident of Moroccan origin, was arrested in Brussels four days before the March 22 bombings on the city's metro and its international airport. He was on the run for four months and had been transferred to France in April for trial.

Abdeslam's detention conditions at a prison in the Parisian suburb of Fleury-Merogis amounted to "psychological torture," former lawyer Mary said, adding that they have contributed to his further radicalization.

He is kept in solitary confinement and subjected to round-the-clock video surveillance.

Abdeslam is accused of providing logistical support to seven attackers who died at the various locations in Paris they had bombed, including the Stade de France national stadium, the Bataclan concert hall and several bars and restaurants in the French capital.