A Frenchman denied on Thursday his presence in a video showing a beheaded American aid worker and the execution of Syrian soldiers.
In a message posted on his Twitter account, Michael Dos Santos said "I categorically announce that I was not present in the video".
The French government suspect the 22-year-old is one of the two French militants appeared on a 15-minutes video showing the beheading of American aid worker Peter Kassig and the execution of several Syrian slodiers.
Ana Dos Santos, mother of Michael Dos Santos, said she did not believe her son appeared in the Islamic State beheading video.
"The more I see the video, the more I tell myself it's not him,"she told news channel BFMTV.
Citing sources from an Islamist group, David Thomson, a journalist at RFI and author of "French Jihadists", believed the man appeared on the video was a Syrian fighter.
Michael Dos Santos is from Champigny-sur-Marne, east of Paris. He converted to Islam and left for Syria in August 2013.
With no criminal record, Dos Santos was wanted by French authorities on charges of having ties with "a terrorist organization".
More than 900 French nationals and residents had either joined Syrian civil war or planned to travel to the conflict-torn country, with 36 being killed in the conflict, official data show.
Earlier this week, Paris prosecutor confirmed the presence of Maxime Hauchard, a Frenchman from northern part of the country, at the scene of the beheading.