ISIS fanatics who beheaded backpackers in Morocco shouted "these are your heads, enemy of God" in a horrific video of the execution.

Louisa Vesterager Jespersen, 24, from Denmark, and Maren Ueland, 28, of Norway, were butchered on a hiking holiday after their suspected killers were seen lying in wait only 600 yards away.

Chilling footage circulating on social media shows a woman screaming while a man cuts her neck with what appears to be a kitchen knife.

During the video, the perpetrators cry out: "It's Allah's will" and are heard saying: "This is revenge for our brothers in Hajine in Syria. These are your heads, enemy of God."

A separate clip published today on Twitter appeared to show four men suspected of murdering the tourists pledging their alliance to ISIS leader Abu Bakr al-Baghdadi.

One of them holds a knife as they sit in front of a black and white flag.

While the video hasbeen verified by intelligence analysts, official authorities are yet to comment on the footage.

The video appeared hours after the three men were arrested as they attempted to flee on a bus where they had hid four massive sword-like weapons under their seats.

Wearing hoods and black jackets, the men were sitting at the back of the bus and reportedly offered "no resistance", vg.no reports.

A national security official identified the three suspects to the Associated Press as Abdessamad Ejjoud, born in 1993, Younes Ouziad, born in 1991, and Rashid Aftati, born in 1986.

They had knives and slingshots when they were arrested, the official said.

Their arrest comes more than three days after French hikers found the victims dead at their camp around six miles from the village of Imlil.

Today's arrests came after police seized their first suspect on Tuesday after he left his ID in a tent close to the scene.

The brutes had beheaded one woman while the second had sustained a serious throat wound.

All four men have sworn allegiance to ISIS, according to a source quoted in Norwegian newspaper vg.no.

A Danish intelligence service spokesman said “The video and preliminary investigation according to the Moroccan authorities indicate that the killings may be related to the terrorist organisation Islamic State.

“This is a case of an unusually bestial killing of two totally innocent young women.”

Moroccan authorities earlier announced they were treating the murders as acts of terror, as the Rabat public prosecutor's office confirmed that at least one of the men is affiliated to a terrorist group.

In the chilling video, the suspects can be heard shouting "it's Allah's will" in a chilling video showing a woman being butchered.

The men are heard referencing Hajin - an ISIS stronghold seized by US-backed forces this week - as an apparent justification for the atrocity.

But the authenticity of the video has still not been confirmed.

A police source told the Reuters news agency that the video appeared to have been filmed in a different place from where the bodies were found.

Today Danish Prime Minister Lars Loekke Rasmussen said the crimes were "politically motivated and thus an act of terror".

"What should have been a holiday trip turned into a nightmare," he told reporters.

"There are still dark forces that want to fight our values", he said, adding: "We must not give in."

Maren and Louisa were in the middle of a month-long holiday when they pitched up in an isolated area at the foot of Mount Toubkal, the highest peak in North Africa.

Prior to their hike, Maren and Louisa stayed for a week in a cheap hotel in the heart of Marrakech, vg.no reports - raising concerns that they were followed by their killers from the city.

Hotel workers in the Moroccan capital claimed Maren and Louisa were staying with three other girls and were spotted with local men before they set off on their mountain trek.

One hotelier said: “Three homeless men came from Marrakech and pitched a tent right next to the girls’ tent. The men were not from round here.”

"Witnesses saw the group at night as they were heading to the camp area.”

Cops have released pictures of the three of the four suspects linked to the murder but have not yet confirmed their names.

Morten Bøås at the Norwegian Department of Foreign Affairs has said that the killings were unlikely to be the work of more established terrorist groups.

He told aftenposten.no that he thought the group of men may have been inspired by ISIS or radicalised through the web.

It’s thought that the men may have stalked the pair before attacking them while they slept on Monday.

CCTV footage showed them setting up camp 600 yards from where the women were sleeping - and later leaving the area at 3am on Monday morning.

A source told Morocco World News: “The suspects were camping in the same area that the murder took place.

"Witnesses saw the group at night as they were heading to the camp area.”

Maren's mum told Norwegian broadcaster NRK that her daughter was "warm and engaged".

She said: "Her first priority was safety. The girls had taken all the precautionary measures before embarking on this trip."

Louisa had posted on Facebook ahead of her upcoming trip, writing: "Dear friends, I'm going to Morocco in December.

"Any of you guys who's around by then or any mountain friends who knows something about Mount Toubkal?"

Both women were studying outdoor activities and cultural guidance at the University of Southeastern Norway and attended a campus in Boe, west of Oslo.

In a statement, Norwegian Prime Minister Erna Solberg said: "This is a brutal and meaningless attack on innocent people, which we react to with disgust and condemnation."

Compared to other countries in North Africa, Morocco has been largely insulated from militant attacks.

The most recent took place in April 2011, when around 17 people were killed in a bombing of a restaurant in Marrakech.

An anti-terrorism rally is planned for Morocco's capital Rabat for Saturday.