Moroccan King Mohammed VI told visiting UN envoy for the Western Sahara Christopher Ross on Wednesday he was concerned by increased security threats in the Sahel.

In particular, the king said the continuing failure to end the conflict in the Western Sahara could "be a factor in the aggravation of these security risks," according to the royal palace.

On Monday, UN leader Ban Ki-Moon called for urgent international efforts to end the Western Sahara conflict because of fears the Mali war will spill over into the Moroccan-occupied territory.

He called on the UN Security Council to strengthen the UN peacekeeping mission in Western Sahara, where Morocco and the Polisario Front have been locked in a more than two-decade showdown over control.

While headlines are dominated by the year-old conflict in Mali, where French-led international forces are battling jihadist groups, many African leaders consider Western Sahara to be the continent's "forgotten conflict".

Morocco started to annex Western Sahara in 1975 as Spanish colonisers withdrew. The Polisario took up arms demanding an independent state until the UN brokered a ceasefire in 1991, but Rabat is only offering autonomy.

Ross, who is in the region in a new bid to mediate between Morocco and the Polisario Front, also spoke of the "urgent need" to solve the conflict.

During Wednesday's meeting in the central city of Fez, the king said the Moroccan proposal for autonomy was an "open and credible solution".

He also reiterated Morocco's desire for an improvement in relations with neighbouring Algeria, which backs the Polisario.