Sahrawi activists blasted Morocco on Friday for failing to probe the disappearance of relatives in Western Sahara, after Spanish experts reported finding the graves of eight civilians executed decades ago.

The team of researchers from Spain's University of the Basque Country exhumed the remains of eight Sahrawis, including two children, conducted forensic tests, and interviewed relatives and witnesses, according to the report published this week and seen by AFP.

The eight Sahrawis, who were individually identified by name, were arrested in February 1976 by a Moroccan military patrol and executed on the spot before being buried in shallow graves, the report concluded.

The researchers carried out their work after a shepherd discovered human remains in April this year in the Fadret Leguiaa area of the disputed territory that is controlled by the pro-independence Polisario Front.

The report was presented in Rabat on Friday by Ghalia Djimi, the vice-president of Sahrawi rights group ASVDH.

It said no light had previously been shed on the case by the Equity and Reconciliation Commission, set up in 2004 by King Mohamed VI to investigate alleged human rights abuses committed under the reign of his father, Hassan II.

And the information provided by another state-run body, the Consultative Human Rights Council (CCDH) on just four of the victims, which claimed that they all died in custody, "has also been proven false".

Contacted by AFP, an official with the National Council for Human Rights, which replaced the CCDH, said he was unable to comment.

Djimi, the Sahrawi group's vice-president, said she and others had waited at least seven years for a response from the Moroccan authorities to a request for an inquiry into the fate of their relatives who disappeared in the Moroccan-controlled part of the region.

"We are convinced that there is no willingness on the part of the Moroccan state to investigate the reality of what happened to those who disappeared," she said.

Amnesty International renewed its call for the UN peacekeeping force in the Western Sahara to be given a human rights monitoring mandate, and said "independent, impartial and thorough" inquiries were needed.

The revelations by the Spanish team "underscore the continuing need to uncover the full truth about hundreds of cases of enforced disappearance from previous decades and to ensure justice for victims and their families," the rights group added.

Morocco occupied the Western Sahara, a former Spanish colony, in 1975 in a move never recognised by the international community, and has proposed broad autonomy under Moroccan sovereignty for the region.

But this is rejected by Polisario Front rebels, who took up arms to fight for an independent state until the United Nations negotiated a ceasefire in 1991, and who insist on the Sahrawis' right to a UN-monitored referendum on self-determination.