WARNING: This article contains graphic content and may be distressing to some readers.

The mother of a Norwegian tourist killed by alleged Islamic extremists in Morocco earlier this week has had her Facebook page flooded with graphic images of her daughter’s remains.

Irene Ueland‘s daughter Maren Ueland, 28, from Norway and her friend Louisa Vesterager Jespersen, 24, from Denmark were both killed while trekking in mountains of southern Morocco. Their mutilated bodies were discovered on Monday near the village of Imlil near Mount Toubkal.

The two Scandinavian women, who were university friends, had set off on a trip on December 9 for a month-long trip in the Morocco and were experienced hikers.

The Morocco murders are being treated as an act of terror, with the BBC reporting that on Tuesday a suspect was arrested who “belonged to a militant group in Marrakesh” and 3 other men were arrested the following day. Overnight, nine other men have been arrested in relation to the crime, bringing the total to 13.

A video allegedly showing two men slashing Jespersen’s throat with a large knife has been circulating online, despite calls for the graphic and disturbing video to be removed. According to Morocco World News, one of the suspects can be heard saying in Darija (Moroccan Arabic): “This is a revenge for our brothers in Hajin”, which is a small Syrian town liberated from ISIS control a fortnight ago by Syrian Democratic Forces.

The Danish Security and Intelligence Service hasn’t confirmed the authenticity of the footage, saying in a press release: “The police and the intelligence agency are still analysing the video. So we cannot at this time say anything about the authenticity of the video.”

News Corp reports that Irene Ueland’s Facebook page has been flooded with disturbing images of both Ueland and Jespersen’s severed and partially severed heads by hundreds of people, with some appearing to be Moroccan nationals demanding that the killers be brought to justice.

The outlet adds that it is not known where the photos were obtained.

Leaders of Denmark and Norway have condemned the attack, with Danish prime minister Lars Løkke Rasmussen calling it a “beastly crime” and the PM of Norway, Erna Solberg, denouncing the “brutal and meaningless attack on innocents”.

Morocco’s prime minister, Saadeddine Othmani, said it was a “stab in the back of Morocco and Moroccans”.