A ship carrying disputed Sudanese crude remained anchored off southwest Japan on Tuesday, February 21 despite a British court ruling giving the tanker permission to unload, three shipping sources said, according to Reuters.

The Ratna Shradha, which is owned by India Steamship, is holding 600,000 barrels of crude oil that South Sudan says was seized by neighbouring Sudan last month and which sold it at deep discount to a North Asian trader, the sources said.

The tanker has yet to receive permission to dock from JX Nippon Oil & Energy, operator of the Kiire terminal, a source familiar with the matter said.

The tanker has remained off the terminal since February 14. The docking schedule for this week does not show the Ratna Shradha unloading. At least two traders said the cargo had been bought by JX Nippon Oil and Energy.

Chambal Fertilisers submitted the case to a British commercial court on February 15, a court official told Reuters, after questions over the legal ownership of the crude emerged. The defendants in the case are listed as the Republic of Sudan, the Republic of South Sudan and Union de Banques Arabes et Francaises, the official added.

Geneva-based Trafigura, the world's third largest oil trader, bought oil which the South Sudanese government claims was seized by its northern neighbour Sudan.

Landlocked, war-ravaged South Sudan must pump oil to the Red Sea via a pipeline across its northern neighbour to Port Sudan. Oil revenues account for 98 percent of the seven-month-old country's income.

The Ratna Shradha is one of at least three tankers that are part of some $815 million in oil revenues that South Sudan's President Salva Kiir accused Sudan of "looting" and which the government in Khartoum said provided compensation for unpaid transit fees.

Sudan has confiscated more than 6 million barrels of South Sudan's oil since December due to the row over oil transit fees, a South Sudanese official said last week.