Rabat - Western Sahara is a former Spanish colony mainly controlled by Morocco, but whose territory is claimed by the pro-independence Polisario Front.Morocco says the territory - which is home to large reserves of phosphate and rich fish stocks off its coast - is an integral part of the kingdom.But the Algeria-backed Polisario Front, which campaigns for independence, demands a referendum on self-determination for the desert territory of half a million residents.Morocco and the Polisario fought for control of Western Sahara from 1974 to 1991, when Rabat took over the territory before the signing of a UN-brokered ceasefire.The Polisario controls around a third of the territory, along the Algerian and Mauritanian borders.Morocco-Algeria tensions Western Sahara is the only territory on the African continent whose post-colonial status has still not been resolved.The conflict continues to poison relations between Morocco and Algeria, whose borders have been closed since 1994.Located on the Atlantic coast, the Western Sahara covers 266 000 square kilometres.Barriers In 1975, the International Court of Justice in The Hague ruled in favour of an independence referendum. The late Moroccan king Hassan II encouraged some 350 000 Moroccans armed with the Koran and the national flag to march to the border with Western Sahara in a show of support for Morocco's annexation of the territory. On February 27, 1976, the Polisario, founded in 1973, proclaimed the Sahrawi Arab Democratic Republic (SADR). Brahim Ghali has led the movement since July 2016, after he took over from historical leader Mohamed Abdelaziz.In 1979, Morocco took control of most of the Western Sahara after Mauritania gave up its part of the territory.Morocco has built six mostly sand barriers along roughly 2 700 kilometres to cordon off areas of the territory it controls.Limbo An independence referendum has been regularly put off since 1992 due to persistent disagreements over the electoral roll.A UN mission, MINURSO, has been in place since 1991 to oversee the ceasefire in Western Sahara.Its headquarters are in the main city of Laayoune, and its relations have been strained with the Moroccan authorities.Morocco quit the then Organisation of African Unity in 1984 after the bloc admitted the SADR as a separate member, but was readmitted by the African Union in January.New UN envoy On April 28, the UN Security Council adopted a resolution backing a resumption of peace talks and extended the mandate of MINURSO by a year.The withdrawal of Morocco and the Polisario from the buffer zone of Guerguerat, a no man's land on the border with Mauritania, boosted hopes of a negotiated end to the conflict.On August 16, former German president Horst Koehler was named new UN envoy to Western Sahara. He was in Morocco on Monday as part of a regional tour aimed at resuming peace talks.