The main suspect in the shooting of four people at the Jewish museum in Brussels was a torturer for Islamic State, according to a French journalist who was held captive by the terrorist group.

Nicolas Hénin, a journalist who was kidnapped in Syria in 2013 and later released in April, said Mehdi Nemmouche was one of the Islamic State’s most feared captors and regularly tortured his prisoners.

Mr Hénin was held together with the American journalists James Foley and Steven Sotloff, who were later murdered by Isis.

He said: “[Nemmouche] was a member of a small group of French nationals whose arrival used to terrify about 50 Syrian prisoners held in cells near ours.

“Every night, blows would start raining down in the room where I myself had been interrogated. The torture went on all night long, until the dawn prayer.”

Mr Hénin also told the weekly magazine Le Point that “when when Nemmouche wasn't singing, he was torturing”.

Last week the terror threat level in the UK was raised to “severe” meaning that an attack on the country is “highly likely”.