"Adrien Guihal, known as Abu Osama al-Faransi, is still under investigation," said the source, speaking on condition of anonymity because they are not allowed to speak to the media.

Guihal "was brought to Iraq two months ago with another 46 French nationals that will be tried here," the source added.

A veteran member of France's jihadist networks, Guihal made headlines when he was recognised as the man behind the voice that claimed responsibility for the July 2016 attack that killed 86 people in the French city of Nice.

He is thought to be among the most dangerous members of the French contingent in the ranks of the Islamic State group (IS), whose self-styled "caliphate" spanned huge swathes of territory in Iraq and Syria before collapsing in 2019.

Guihal, who joined IS in 2015, was detained in the Syrian city of Raqa in May 2018.

He spent years in Kurdish prisons in Syria before being brought to Iraq in July, along with 46 other French nationals who are being questioned over their alleged involvement in crimes committed by IS in Iraq.

"Interrogations are ongoing with the 47 French nationals," the Iraqi source said, alleging that "it has been proven" they are all members of IS.

Last week, Iraq's National Intelligence Service said the suspects were "wanted by the Iraqi judiciary for their involvement in terrorist crimes committed in Iraq".

Iraqi courts have handed down hundreds of death sentences and life prison terms to people convicted of terrorism offences, including hundreds of foreign fighters -- some caught in Syria and transferred across the border.

In 2019, the courts sentenced 11 French nationals to death, all of whom remain on death row.