Rival protests were held on Friday outside a military tribunal in the Moroccan capital where 24 Sahrawis accused of killing members of the security forces in the Western Sahara in 2010 are in the dock.
The politically charged trial, which is being attended by a number of independent foreign observers, has been repeatedly delayed, with the defendants held in custody for more than two years.
The authorities say 11 people died in the clashes, among them members of the security forces, which broke out as the army moved to dismantle the Gdim Izik camp where thousands of local Sahrawis were living in November 2010.
The Sahrawis arrested during the unrest are accused of violence against the security forces, of pre-meditated killing and of mutilating victims' bodies.
Some 100 people demonstrated outside the court in Rabat on Friday, among them families of the victims, pro-Sahrawi activists and relatives of the accused, many of whom were allowed to attend the trial, an AFP journalist said.
Some relatives of the victims remained outside the tribunal, waving banners that read: "We know who the killers are, so where is justice?"
Ahead of the trial, observers and rights groups expressed concern over allegations the defendants were tortured in custody, about the case being tried by a military court, and about the possible death penalty facing the accused, if convicted.
"Allowing a military court to try civilians raises doubts about the fair, independent and impartial administration of justice," said the Naples-based International Observatory for Human Rights in a statement.
A judicial source, quoted by official media, said the accused were being tried in a military court because they had committed "criminal acts against the military and security forces."
Michael Ellman, a British human rights lawyer familiar with the case, who is attending the trial as an independent observer, said he had seen "many statements" provided by relatives detailing marks of torture on the defendants.
"I have no reason to doubt them," he told AFP, adding: "Most of the suspects haven't been able to see a doctor."
At dawn on November 8, 2010, Moroccan security forces moved to dismantle the Western Sahara camp, near the territory's main city of Laayoune, which thousands of Sahrawis had set up in protest over their living conditions.
The intervention sparked clashes that spread to Laayoune, where businesses and public buildings were looted and torched.
The authorities said 11 people were killed in the unrest, while the Algeria-based Polisario Front separatists said dozens of people lost their lives.
Morocco, whose annexation of the former Spanish colony in 1975 is not recognised by the international community, has proposed broad autonomy for the territory under its sovereignty.
This is rejected by the Polisario Front, which insists on the right of the Sahrawi people to a referendum on self-determination and launched its struggle for independence even before the annexation.
The resulting war lasted until 1991 when the United Nations brokered a ceasefire, but a permanent settlement remains elusive.
UN peace envoy Christopher Ross began a new round of international diplomacy this week aimed at resolving the conflict, after his efforts to break the deadlock with a series of informal talks between the two sides made no progress.