South Sudan sold via tender a cargo of Nile Blend crude for December loading at the highest premium in at least four years as fears of possible confrontation with neighbouring Sudan drove up prices, traders said on Tuesday.

In a sign of new tensions, Sudan on Saturday said it had submitted a new complaint against South Sudan to the United Nations Security Council, accusing it of supporting rebels in two border states in a sign of new tensions between the former civil war foes.

South Sudan sold the 600,000-barrel cargo to Chinaoil at a premium of US$1.20 a barrel to Indonesia Crude Price (ICP) Minas, they said.

It also sold a second cargo to European trading company Trafigura at a premium of 90 cents a barrel to ICP Minas, traders said.

Nile Blend's spot premium last surged more than $1 a barrel in 2007 when a massive earthquake rocked Japan, they said.

The heavy sweet crude is popular among North Asian refiners and is typically processed in complex refineries to produce feedstock for fluid catalytic crackers.

Spot discounts for another Sudanese crude, Dar Blend, have also narrowed in recent months.

In a separate tender, South Sudan sold 3.8 million barrels of Dar Blend crude for December loading at a narrower discount than the previous month, partly on stronger fuel oil cracks.

The cargoes were sold to Chinaoil, Unipec and Vitol at around $8 a barrel below dated Brent, traders said.