Moroccan troops and separatists square up in Western Sahara

Tensions are brewing in the troubled Western Sahara region, as Moroccan troops and Sahrawi separatist fighters refuse to budge from a sensitive buffer area.

UN Secretary-General Ban Ki-moon has urged both sides to withdraw from the strip of no man's land close to the Mauritanian border, amid fears that militarisation of the territory could flare up into war.

Mauritania has reportedly deployed anti-aircraft missiles close to the Moroccan border fearing all-out conflict might break out at any moment.

The UN chief seems similarly concerned that a 16-year truce is about to fall apart.

"[I'm] deeply concerned over the tense situation that has developed in the narrow buffer strip in southwestern Western Sahara," he said.

Moroccan soldiers and Polisario fighters were "in close proximity to each other" in the buffer zone, a UN statement has said.

Ki-moon called on both sides "to suspend any action that alters that status quo and to withdraw all armed elements so as to prevent any further escalation".

The UN mission in Western Sahara - known as MINURSO - will hold discussions with both sides to de-escalate tensions, he added.

A 1991 ceasefire between Morocco and the Polisario ended 16 years of fighting between Rabat and the Polisario Front.

It left the Morocco controlling of all of the territory's main towns and the Polisario confined to a narrow strip of the desert interior.

[I'm] deeply concerned over the tense situation that has developed in the narrow buffer strip in southwestern Western Sahara. - UN chief Ban Ki-moon

The far south was left as territory neither side could have a permanent military presence.

According to the truce arrangements no troops should enter the buffer strip.

Earlier this month, the Polisario complained that Morocco had violated the ceasefire agreement and entered the territory.

Rabat admitted that troops were in the buffer zone, but were there to stop cross border smuggling of stolen and second-hand vehicles.

Western Sahara has been a trouble spot for years, with Rabat insisting the territory is an integral part of the kingdom, while the UN had ruled that a referendum on self-determination should be held.

Relations between Morocco and the UN have been strained after Ban used the term "occupation" to describe the status of the disputed territory.

Morocco responded by expelling dozens of UN personnel in the territory in March, and only allowed about 25 to return.

Agencies contributed to this story.