Two dozen suspects have gone on trial in Morocco over the murder of two young Scandinavian hikers last year that shocked the north African country.

24-year-old Danish student Louisa Vesterager Jespersen and Norwegian Maren Ueland, 28, were beheaded in December at an isolated site in the High Atlas mountains.

Three main defendants accused of direct involvement in the murders, who allegedly pledged allegiance to the so-called Islamic State jihadist group, could face the death penalty.

24 defendants - 23 of whom are Moroccan men - appeared in court in Sale to answer charges including promoting terrorism, forming a terrorist cell and premeditated murder.

A Spanish-Swiss convert to Islam is also among the suspects facing justice in the city near Rabat.

Court officials said the opening session of the case was immediately adjourned until 16 May to give the defence more time to prepare.

The families of the two victims and their lawyers are not expected to attend the trial.

Nature lovers, Ms Jespersen and Ms Ueland shared an apartment and went to Norway's Bo University where they were studying to be guides.

The friends had travelled together to Morocco for their Christmas holidays.

They were killed in the foothills of Toubkal, the highest summit in North Africa, some 80km from the city of Marrakesh, a tourist magnet.

After the bodies were discovered, the Moroccan authorities were initially cautious, referring to a "criminal act" and wounds to the victims' necks.

But that changed when a video showing one of the victims being beheaded - filmed by one of the apparent killers on a mobile phone - circulated on social networks.

Moroccans pay tribute to murdered hikers in front of the Danish embassy in Rabat

One of those in the footage refers to "enemies of Allah" and revenge for brothers in Syria.

The video did the rounds online in Morocco, Norway and Denmark.

Danish police last month launched prosecutions against 14 people suspected of sharing the footage.

A separate video in the initial aftermath of the murder showed the alleged killers pledging allegiance to IS leader Abu Bakr al-Baghdadi.

Investigators said the "cell" was inspired by IS ideology, but Morocco's anti-terror chief insisted the accused had no contact with the jihadist group in conflict zones.

IS has never claimed responsibility for the double-murder.

Abdessamad Ejjoud, a 25-year-old street vendor referred to as the emir of the group by peers, is the suspected ringleader, according to investigators.

Police quickly arrested a first suspect in the suburbs of Marrakesh, and three others were arrested a few days later when they tried to leave the city by bus.

Aged from 25 to 33, all had struggled to get by in poor districts of Marrakesh.

They had recently embraced Salafism, an ultra-conservative branch of Sunni Islam, according to friends, neighbours and some family members.

Petitions on the internet have called for anyone convicted of the double murder to face the death penalty.

But a de facto moratorium on carrying out executions has been in place since 1993.

A second Swiss citizen arrested after the double-murder was tried separately and jailed in mid-April for ten years on charges including "forming a terrorist group".