Parents of James Foley, the US journalist beheaded by the Islamic State (Isis) in 2014, are deeply disturbed after France's far-right leader Marine Le Pen tweeted an image of their son's beheaded body.

Le Pen posted the image after her political party was accused of sharing "community of spirit" with Isis. A journalist said her Front National Party bore similarities to the radical extremist group, the Guardian reported.

In an attempt to set the record straight, the far-right French leader posted three images of Isis killings on Twitter. "Daesh is THIS" Pen wrote in a series of angry tweets, using the Arabic acronym for the group.

But her attempt at providing a distinction between her party and the Islamic State backfired: Foley's parents said they were "disturbed" by the incident, according to the Guardian.

"Our family was informed this morning that Marine Le Pen, a French politician, tweeted a shamefully uncensored picture of our son. We are deeply disturbed by the unsolicited use of Jim for Le Pen's political gains and hope the picture of our son, along with two other graphic photographs, is taken down immediately," Diane and John Foley said in an official statement.

An investigation into "the dissemination of violent images over the tweets" has been launched by the prosecutor's office in a western suburb of Paris, reported the Guardian.

Le Pen's party suffered a humiliating defeat in regional elections on Sunday.

Attacking Le Pen, a journalist, Jean Jacques Bourdin, said on BFM TV Pen's Front National Party and Isis both focused on identities, hence they shared "a communist spirit", said the Guardian stated. 

Le Pen posted the images as an answer to Bourdin. France Interior Minister Bernard Cazeneuve called the images, "propaganda of Daesh," as per the Guardian report.

James Foley, a US freelance journalist, was captured by the Isis militants in Syria in 2012. Two years later, he was beheaded by the extremist group in 2014.