Thousands greeted the king in the region

On Thursday, thousands of people bearing flags and banners lined up on the streets of Dakhla and Laayoune to greet the king.

But the Polisario Front movement, which has been demanding autonomy for Western Sahara for 25 years, called the king's visit unlawful and provocative.

It even warned that the trip could bring about a "deterioration of peace".

The visit comes in the aftermath of fresh protests by the Polisario Front, which has been particularly angered by Morocco's recent oil exploration deals with French and US oil companies to work off the Saharan coast.

Rifts

The trip also comes amid rising diplomatic tensions between Morocco and Spain.

Morocco recalled its ambassador to Spain at the weekend.

The move is apparently a protest against Spain's refusal to back a French initiative that would have strengthened Morocco's claim to Western Sahara.

The Polisario Front rejects the latest referendum plan

The United Nations does not recognise Moroccan sovereignty over the region, but efforts to resolve the dispute by a referendum of its population have faltered.

In addition, three Spanish non-governmental organisations (NGOs) last week organised a symbolic referendum in the southern Andalusia region as part of a campaign in favour of the Polisario.

Correspondents say that the king's current visit appears aimed at asserting Moroccan authority over the region.

Autonomy plan

In June, the Moroccan Government agreed to a UN plan proposing autonomy to Western Sahara as a basis for negotiations on a final settlement in the 26-year-old conflict.

Baker is mediating on behalf of the UN

The plan conceded much to Morocco, and gave little to the Sahrawi nationalist movement led by the Polisario Front.

The Polisario Movement angrily rejected the plan and threatened to go back to war.

Put together by the UN secretary-general's special envoy to the Western Sahara, James Baker, the plan would have seen Morocco guaranteed sovereignty over the territory for four years, including Moroccan control of internal security and the judicial system.

In exchange, the Sahrawi population were to be given some leeway in controlling their own economic and social affairs.