There are reports that Sudan has sold at least one cargo of crude oil from one of the oil tankers seized from South Sudan worth millions of dollars.

On Monday South Sudan announced it was stopping oil production as it accused Sudan of seizing tankers at Port Sudan, carrying $ 815 million worth of crude oil.

Sudan said it confiscated the tankers as compensation for unpaid transit fees.

South Sudan drills oil in its region, but Sudan operates the pipeline leading north to Port Sudan.

Sources said the shipment of 600,000 barrels has been loaded on to a ship called the 'Ratna Shradna' for a dealer in Singapore.

The final price of the sale remains unknown, but sources told Reuters news agency the shipment was thought to be sold at a discount from standard South Sudan pricing, up to $14 a barrel.