Nairobi  - A lack of transparency in Sudan's oil revenue figures could endanger an uneasy north-south peace deal in Africa's largest nation, campaigning group Global Witness said Monday.

An agreement on sharing oil wealth was a crucial part of the Comprehensive Peace Agreement, which officially ended the 1983-2005 civil war between the Muslim north and Christian and animist south, in which almost 2 million people died.

However, Global Witness says the north, which is responsible for marketing and exporting the oil, may be under-reporting its oil figures and thus giving the autonomous Southern Sudan less money than it should.

"Unless the government of Southern Sudan and Sudanese citizens can verify that the revenue sharing is fair, mistrust will grow and the peace agreement could be jeopardised," Global Witness campaigner Rosie Sharpe said.

According to the group, the figures published by Khartoum for the oil blocks subject to revenue sharing do not match up with those released by the China National Petroleum Corporation (CNPC), which operates the blocks.

The discrepancies ranged from 9 to 26 per cent from 2005 to 2007, Global Witness said.

Global Witness - a UK-based organization that investigates the links between natural resources and conflict - said if the figures had been under-reported by 10 per cent, Southern Sudan would be owed over 600 million dollars.

Southern Sudan receives the overwhelming majority of its revenues from oil.

"The oil production and sales figures upon which the revenue sharing depend should be verified by independent third party audit," said Sharpe.

Global Witness called on the peace deal's guarantors - the UK, US and Norway - to promote transparency and also appealed to Sudan's customers.

"China and Japan, who are the main customers for Sudanese oil, should also push for greater transparency, which will help ensure stability and a reliable supply."

Oil has already brought the two sides back to the brink of war.

Clashes between northern and southern forces in the disputed oil-rich Abyei region last year threatened to reignite the conflict.

However, both sides have said they will abide by a ruling setting the boundaries around Abyei, issued in July by an arbitration court in The Hague.

Tensions have also been raised by tribal clashes in the south, which some officials have accused the north of engineering in order to undermine general elections in 2010.

The elections are a stepping stone to a referendum on independence for Southern Sudan in 2011, which is also enshrined in the peace agreement. (dpa)