The cargo, which was extracted by a Moroccan company, has been claimed by Western Sahara, a former Spanish colony controlled by Rabat where the Polisario Front group is fighting for independence.

Last month, a court in Port Elizabeth, South Africa gave an order granting the auction after a petition from the Polisario Front.

South Africa is a strong supporter of Western Sahara’s struggle for independence.

Morocco’s phosphate industry giant OCP last year accused South Africa of “political piracy” by detaining the ship.

The silent auction of 55,000-tonnes of “high grade phosphate” — originally destined for New Zealand — opened on Monday and will last one month.

“The auction started yesterday,” Kamal Fadel, a representative of Western Sahara — known as the self-declared Sahrawi Arab Democratic Republic — told AFP.

“It is high-grade phosphate. The proceeds will go to the Sahrawi Republic and may be to used to fight similar cases.”

The Polisario Front claims the phosphate on grounds that it was extracted in Western Saharan territory, allegedly in contravention of international principles.

Morocco and the Polisario fought for control of Western Sahara from 1974 to 1991, when Rabat took over the desert territory before the signing of a UN ceasefire.

Rabat considers resource-rich Western Sahara to be an integral part of Morocco, but the Polisario demands an independence referendum.

The Marshall Islands-flagged Cherry Blossom vessel has been held in South Africa since last May when a court ruling blocked the vessel from leaving Port Elizabeth.