- Nicolas Henin tells reporters Mehdi Nemmouche beat him during captivity in Syria
- Nemmouche is accused in the shooting of four people at the Jewish Museum in Belgium
- Henin, a reporter for Le Point, alleges that Nemmouche used to beat and torture prisoners
- Henin was freed in April after 10 months in captivity, part of which he spent with James Foley
A suspected jihadist accused of a deadly shooting at Belgium's Jewish Museum also guarded Western hostages while fighting with ISIS in Syria, according to a French journalist and former captive.
Nicolas Henin -- who was released in April from captivity in Syria -- told reporters Saturday that suspect Mehdi Nemmouche not only was one of his captors, but that he tortured and beat those in his charge.
"I've been given a number of graphic and audio materials that allowed me to be certain that the fighter that I met in Syria during my captivity was indeed Mehdi Nemmouche," he said during a news conference held in Paris.
Henin told CNN he spent seven of the 10 months he was held with beheaded U.S. journalist James Foley, making it possible that Nemmouche would also have come in contact with him.
He told reporters Nemmouche physically assaulted him a number of times during his captivity.
"I don't know of any bad treatment to any other foreign hostages coming from him specifically, but I witnessed him torturing local prisoners," Henin told reporters.
Nemmouche is currently in Belgium, having been extradited from France in July. He awaits prosecution in the fatal shooting of four people at the Jewish Museum in Brussels in May.
Henin's accusation against Nemmouche first surfaced in a piece published Saturday in Le Point.
Le Point, Henin's employer, said it had not planned to go public with Henin's information because they worried that doing so could jeopardize the safety of about 20 Western hostages still held by ISIS in Syria. But a report Saturday by French newspaper Le Monde that made public Nemmouche's alleged involvement in hostage-taking forced its hand.
French Interior Minister Bernard Cazeneuve told reporters in Montpellier on Saturday that French officials believe Nemmouche "could have been the jailer of hostages, including our hostages."
CNN has not been able independently to verify the allegations.
An attorney for Nemmouche, Apolin Pepiezep, declined to comment when contacted by CNN. But he told France-based BFM-TV that he thinks the journalist is confusing his client with someone else.
Pepiezep confirmed his client was questioned by French authorities this summer, but was not asked about that period in Syria.
Portrayal of lost, perverse young man
Le Monde reports that the French internal security directorate, the DGSI, passed information to the counterterrorism section of the Paris prosecutor's office on Nemmouche's suspected role based on testimony from former hostages.
The witness accounts vary, the newspaper reports, with some saying it was "possible" Nemmouche was one of the captors, while others were more certain.
According to certain witnesses, Le Monde says, Nemmouche was only a lowly member of ISIS tasked with guarding the Western hostages -- but he showed great brutality and committed serious abuses.
The account given by Henin -- one of four French hostages released in April -- to Le Point appears to bear out that characterization.
It paints a picture of Nemmouche as an egotist and storyteller, a lost, perverse young man who sees jihad as a route to the notoriety he craves. He allegedly guarded Western hostages then held in a former hospital in Aleppo, Syria, that had been transformed into a prison. Henin says he was his captor between July and December of last year.
"When Nemmouche was not singing, he would torture," Henin is quoted as saying. He alleges Nemmouche was part of a small group of French jihadists who would terrorize about 50 Syrian prisoners held in the neighboring cells.
"Every evening, the blows would start to rain down in the room where I myself had been interrogated," he recalls. "The torture lasted all night, until the dawn prayer. The screams of the prisoners were sometimes met by yelps in French."
Henin's full account of his experiences in captivity is due to be published next week by Le Point.
Prosecutors: Suspect found with revolver, Kalashnikov
Cazeneuve, the French interior minister, said that as soon as the freed hostages gave information to the DGSI about Nemmouche, "it was immediately communicated to (officials) so that justice could follow its course."
He added, "This was done in extremely discrete manner to facilitate the efficiency of the procedures in the face of a character who is extremely violent ... and represented a danger to the safety of French people."
French prosecutors said at the time of Nemmouche's arrest that he had been found in a check on a bus entering Marseille with a checked bag containing a revolver, a Kalashnikov and a small GoPro camera like the one seen on the suspect in the museum shooting.
The 29-year-old, from Roubaix in the Pas-de-Calais region of northern France, recently spent a year in Syria and is a radicalized Islamist, the chief prosecutor of Paris said at a news conference.
François Molins said Nemmouche, who has a criminal history that included a five-year prison stint, was influenced by Islamist teachings while in prison and left for Syria three weeks after being released in September 2012.
Also found in the bag, according to Molins, was "a white cloth with words written with a marker, mentioning in Arabic the Islamic State in Iraq and Levant," as ISIS is also known.
Foley 'had to endure more'
Henin told CNN last month that he and Foley had been mistreated at times by their captors while held together.
"Foley especially had to endure more because he was American," he said. "He was missing his family and would talk often about them."
Foley's killing was followed days later by another video showing the beheading of another American journalist held by ISIS, Steven Sotloff. A threat was made at the end of the video to a British hostage in the group's hands.
Henin was freed along with French photographer Pierre Torres and two other French journalists, Didier François and Edouard Elias, on April 19.
It's not known what went on behind the scenes to secure their release, but French Foreign Minister Laurent Fabius insisted that France had not paid a ransom, Radio France Internationale reported at the time.