Updated

A young Frenchman is believed to be among the killers on an Islamic State propaganda video showing a beheaded American aid worker and the deaths of more than a dozen Syrian soldiers, France's top security official said Monday.

Interior Minister Bernard Cazeneuve said there is a "strong presumption" that Maxime Hauchard is among the group of Islamic extremist fighters in the video released over the weekend. He urged young people in France to "open your eyes to the terrible reality" of the militant group.

Cazeneuve said authorities were analyzing the video and have been investigating Hauchard, who is around 22 years old and from west of Paris. The convert to Islam gave an interview to France's BFM television in July, telling the network he had helped in the capture of Mosul, the Iraqi city whose fall eventually prompted the United States to resume military operations there.

"I call solemnly and seriously on all our citizens, and notably our young people who are the primary target of the terrorist propaganda, to open your eyes to the terrible reality of the actions of Daesh," Cazeneuve said, using an Arabic acronym for the group. "These are criminals that are building a system of barbarity."

French citizens make up the largest contingent of European jihadi fighters who have joined extremists in Syria and Iraq. According to the Paris prosecutor's office, about 1,100 people have been placed under surveillance, and 95 people face charges.

Hauchard, who is believed to have arrived in Syria in 2013, is among those under judicial investigation, Cazeneuve said.

In the July interview, Hauchard said he was expecting and hoping for death.

"From a personal point of view, my objective is to be a martyr," Hauchard said.