Updated

Moroccan authorities have arrested three more suspects in the killings of two Scandinavian tourists in Morocco's Atlas Mountains, as the Danish intelligence agency said it "may be related" to the Islamic State group.

Morocco's Central Office of Judicial Research said in a statement Thursday that the three new suspects were arrested in Marrakech. Another suspect was arrested Tuesday, and a Moroccan prosecutor said he had affiliations to an extremist group, without naming it.

The killing can be considered "politically motivated and thus an act of terror," Danish Prime Minister Lars Loekke Rasmussen said Thursday. He said "there are still dark forces that want to fight our values" and "we must not give in."

He confirmed the victims' identities as Louisa Vesterager Jespersen of Denmark, and Maren Ueland from Norway.

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

In neighboring Norway, Prime Minister Erna Solberg called the slaying "a brutal and meaningless attack on innocent people," adding the case "emphasizes the importance of combating violent extremism."

In a statement to The Associated Press, Denmark's domestic security agency said the preliminary investigation "indicate, according to Moroccan authorities, that the killings may be related to the terrorist organization the Islamic State group."

The killing has shocked Morocco, a popular tourist destination where attacks on foreigners are extremely rare. The women's bodies were found Monday in the Atlas Mountains, an area prized by hikers.

The bodies were found in a remote mountainous region, 10 kilometers (six miles) from the village of Imlil — often the starting point for treks to Mount Toubkal, North Africa's highest peak.

Moroccan media outlets reported that investigators have video surveillance footage showing three suspects putting up a tent near the victims' tent and leaving the area after the slaying.

The mayor of the Norwegian victim's Time, Reinert Kverneland, told Norwegian broadcaster NRK that he informed relatives of the death. The victim's mother, Irene Ueland, told NRK that her daughter had taken safety precautions before making the trip.

Authorities in Denmark and Norway on Wednesday warned their citizens from hiking without local guides in Morocco after the killing. Danish police officials said Wednesday they sent an officer to Morocco to assist in the investigation.

Morocco is generally considered safe for tourists but has battled for years with Islamic extremism for years, and thousands of Moroccans joined the Islamic State group.

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Amira El-Masaiti reported from Rabat, Morocco.