A video purportedly showing the killings of two Scandinavian tourists in Morocco by suspected Islamist State militants is probably authentic, Norwegian police said on Friday.

The bodies of Louisa Vesterager Jespersen, 24, from Denmark, and Maren Ueland, 28, from Norway were found on Monday in the Atlas Mountains, on the way to Toubkal, North Africa's highest peak and a popular hiking destination.

Moroccan authorities have said four suspects arrested over the murder had pledged allegiance to Islamic State in a video posted on social media before the killings.

The women were found with knife wounds to the neck, Morocco said.

A separate video of the actual deaths, also on social media, was likely to be real, Norwegian police said.

"When it comes to the assessment of the video that purportedly shows the killings, there is still a certain amount of technical analysis and assessment to be done," Norway's National Crime Investigation Service said in a statement.

"We still believe, however, that we have grounds to say that so far, there is nothing concrete to show that this video is not real."

Norwegian police were not immediately available for further comment, while their Danish counterparts said they were was still analysing the video.

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

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