Morocco on Friday expelled four French human rights campaigners who it accused of trying to help independence activists in the disputed territory of Western Sahara, drawing condemnation from Amnesty International.

The four were arrested in the southern Moroccan town of Tan-Tan and held by police before being taken to Agadir airport and put on a plane to Paris, a Moroccan security source said.

"The police services in Tan-Tan proceeded on Friday to expel from the national territory the four French citizens who represent a risk to public order," said the source.

One of the four, Claude Mangin-Asfari, planned to organise a visit by international human rights groups to the territory and "help the separatists", the source added.

"Amnesty International deplores today's expulsion by the Moroccan authorities of a delegation of Action by Christians against Torture as another setback against human rights defenders working on Western Sahara," the London-based rights group said in a statement.

Morocco annexed the resource-rich former Spanish colony in 1975, triggering a war with independence movement Polisario until 1991 when the United Nations brokered a ceasefire.

The UN has tried to hold a referendum to allow Sahrawis to decide their future but Rabat says the vote is impossible to organise and the most it will offer is limited autonomy.

No country recognises Morocco's claim over the territory larger than Britain, but it has powerful allies. France, Spain and the United States have all voiced support for the autonomy plan while denying any partiality in the dispute.

Sahrawi rights groups say Moroccan police torture, assault and unlawfully imprison those who oppose its presence, something the Moroccan authorities repeatedly deny.

Mangin-Asfari is married to Sahrawi rights campaigner Ennaama Asfari, who was arrested on April 13 in Marrakesh in southern Morocco and charged with drunk driving and assault.

Asfari, who is being held in prison while awaiting his trial on April 28, said he was followed by police for three days before being arrested and that the charges were trumped up by the Moroccan authorities to thwart his activities.

He said he was tied to a tree and beaten while being interrogated about his relations with Sahrawi students in Marrakesh, according to Amnesty.