The move by a judge in Nanterre, just outside Paris, came after the National Assembly voted in November to strip the National Front chief of her parliamentary immunity over the three photos of IS violence posted in 2015.

Le Pen, who lost to Emmanuel Macron in last year's presidential vote, 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.

The crime is punishable by up to three years in prison and a fine of 75,000 euros ($91,000).

The pictures were posted just a few weeks after the Paris terror attacks in November 2015 in which 130 people were killed.

One of the pictures showed the body of James Foley, an American journalist beheaded by the Sunni extremists.

The others showed a man in an orange jumpsuit being driven over by a tank and a man being burned alive in a cage.

"Daesh is this!" Le Pen wrote in a caption, using an Arabic acronym for IS, in response to a TV journalist drawing a comparison between the extremists and the French far-right.

Le Pen later deleted the picture of Foley after a request from his family, saying she had been unaware of his identity.

"I am being charged for having condemned the horrors of Daesh," Le Pen told AFP.

"In other countries this would have earned me a medal."

Parliament had already lifted in September the immunity of another FN lawmaker, Gilbert Collard, over similar tweets containing IS images.

At the time Le Pen, a lawyer by training, denounced the move as a "lowly, purely political decision" which violated her freedom of expression.