A French journalist held hostage in Aleppo has alleged that one of his captors was a Frenchman suspected of an attack on a Jewish museum in Brussels.

Nicolas Henin named Mehdi Nemmouche, a 29-year-old of French-Algerian origin, reigniting concerns about the number of European jihadists fighting with Islamic State in Syria and Iraq.

“After the arrest of Nemmouche for the crime alleged against him by a Brussels judge, I was given a number of audio-visual files that helped me to make a formal recognition,” said Henin.

The report for French magazine Le Point also claimed Nemmouche mistreated him.

“I am not aware of other Western hostages having been mistreated by him. But I did hear him torture Syrian prisoners in the building we were being kept in – it was the basement of a hospital that probably also held between 50 to 80 common law prisoners of Islamic State.”

Henin, who was released in April, said Nemmouche took sadistic pleasure in mistreating prisoners.

Reports suggest the alleged extremist spent more than a year in Syria before returning to Europe in March.

Meanwhile Nemmouche’s French laywer Apolin Pepiezep says his client was never questioned about Syria.

“Nobody asked the question of whether he went to Syria or not. Nobody can say he went there. He’ll never say he never went to Syria and nobody asked him what role he played when was in Syria. It was all about the attack that took place in Belgium.”

CCTV footage from May allegedly shows Nemmouche opening fire indiscriminately at the museum in Brussels , killing four people.

He is now awaiting trial for murder after being extradited from France.