Morocco has defended its security forces following last week's raid at a protest camp in Western Sahara in which at least 12 people were killed.
Interior Minister Taieb Cherkaoui said police intervention at the camp near the town of Laayoune had been peaceful.
He said some Sahrawi protesters had killed members of the security forces using knives and petrol bombs.
The Polisario Front, which seeks independence for Western Sahara, has called on the UN to investigate.
In a letter to the UN Security Council on Monday, Polisario said that more than 36 Sahrawis died in the clash and 163 were detained.
Moroccan officials said 12 people had died, 10 of them members of the security forces.
The Gadaym Izik camp was set up some weeks ago outside the regional capital Laayoune as a protest by displaced Sahrawi people about their living conditions. It was home to more than 12,000 people.
Sahrawi activists insist their protest was peaceful and about social problems such as jobs and housing, not political issues.
But at a joint news conference, Mr Cherkaoui and Foreign Minister Taieb Fassi Fihri showed video footage made by police which allegedly showed a Moroccan policeman's throat being cut.
They said the level of violence was not common among militias in Morocco.
"I am not saying that al-Qaeda is definitely implicated in what happened in Laayoune," Mr Cherkaoui said.
"But the style used and the savagery in which that crime was committed - I mean decapitating a member of the security forces - is something unknown in Morocco and also unknown in the southern provinces."
Morocco annexed Western Sahara - a former Spanish colony - after Spanish settlers pulled out in 1975.
The Polisario Front founded the Sahrawi Arab Democratic Republic (SADR) and waged a guerrilla war against Moroccan troops until a UN-brokered ceasefire in 1991.
Rabat is offering to grant Western Sahara autonomy, but Polisario is demanding a referendum on full independence.