A French judge has opened a formal criminal investigation into Marine Le Pen's publication on Twitter of a series of grisly images in 2015, reports the BBC.
The three images referred to the so-called Islamic State group and were captioned "Daesh is THIS!"
One showed the decapitated body of IS victim James Foley.
The far-right National Front leader later deleted that image amid the resultant outcry, insisting she was unaware of the victim's identity.
The other images showed a tank running over a man in an orange jumpsuit, while another jumpsuit-clad man was shown in a cage being burned alive.
Ms Le Pen is facing charges of circulating "violent messages that incite terrorism or pornography or seriously harm human dignity" and that can be viewed by a minor - punishable by up to three years in prison.
The investigation is the latest blow to the embattled Ms Le Pen, who lost the French presidential election to Emmanuel Macron in May 2017.
After the investigation was announced on Thursday, Ms Le Pen defended her actions, saying she was being charged for condemning IS.
"In other countries this would have earned me a medal," she told AFP.