COPENHAGEN — The authorities in Morocco said on Thursday that three more suspects had been arrested in the killings of two Scandinavian tourists in the Atlas Mountains, in what Danish officials suggested was an act of terror linked to the Islamic State.

The Central Office of Judicial Research in Morocco said in a statement that the three suspects had been detained in Marrakesh. Another suspect arrested on Tuesday was thought to have extremist ties, Moroccan prosecutors told local news outlets without providing further details. The names of those arrested were not immediately released.

The authorities said that the bodies of the victims, Louisa Vesterager Jespersen, 24, of Denmark and Maren Ueland, 28, of Norway, were found on Monday by other tourists in an isolated area of the High Atlas Mountains, an area popular with hikers and six miles from the village of Imlil. Both women had been studying at the same school in Norway to become tour guides.

Prime Minister Lars Loekke Rasmussen of Denmark said on Thursday that the killings might be “politically motivated, and thereby an act of terror.” He added that “there are still dark forces that want to fight our values” and that “we must not give in.”