A Swiss man has been arrested on suspicion of training those who killed two Scandinavian women in Morocco earlier this month.

The bodies of Louisa Vesterager Jespersen, 24, from Denmark and Maren Ueland, 28, from Norway, were found on 17 December in an isolated area near Imlil, on the way to Mount Toubkal, North Africa’s highest peak and a popular hiking destination. They had suffered wounds to their necks.

The man, arrested in Marrakech on Saturday, is the 20th person to be detained over the murders.

He is “suspected of teaching some of those arrested in this case about communication tools involving new technology and of training them in marksmanship”, Morocco’s central office for judicial investigations said.

It added he was involved in the “recruitment of Moroccans and sub-Saharans to carry out terrorist plans in Morocco”. 

Authorities consider the slayings of the young women to be a terrorist act and have confirmed a video exists of the moment at least one of the women was killed.

The killing can be considered “politically motivated and thus an act of terror,” Danish prime minister Lars Loekke Rasmussen said on Thursday.

He added “there are still dark forces that want to fight our values” and “we must not give in”.

Denmark’s domestic security agency said in a statement that a preliminary investigation “indicates, according to Moroccan authorities, that the killings may be related to the terrorist organisation the Islamic State group”.

The development came after authorities in Denmark and Norway warned their citizens from hiking alone without local guides in Morocco.

Danish police have sent an officer to Morocco to assist in the investigation.