Morocco has expelled a Swedish diplomat for passing on official documents to separatist groups active in Western Sahara, its foreign ministry says.

Anna Block-Mazoyer was accused of committing "a serious breach of diplomatic practice", a statement quoted by AFP news agency said.

Documents given to the diplomat during an official briefing reached the separatist Polisario Front, it said.

Sweden's foreign ministry has confirmed it has been informed of the decision.

Despite the four-round UN-backed talks between Morocco and the Algerian-backed Polisario Front, there has been no progress so far in resolving the dispute.

Morocco, which controls most of the Western Sahara, has proposed semi-autonomy for the region.

But the Polisario Front is asking for a referendum with full independence as one of the options.

A ceasefire has held since 1991, but negotiations have stalled many times since then with little common ground between the opposing sides.

The territory is phosphate-rich and believed to have offshore oil deposits. Most of it has been under Moroccan control since 1976.