Civil society leaders in South Sudan are closely watching a legal battle unfolding in Sweden, as prosecutors investigate an oil company accused of involvement in massive human rights abuses.

A suspected Sudanese air strike on a refugee camp in South Sudan will not trigger a return to war but belligerent posturing on both sides will complicate and slow talks over oil transit fees and other sensitive disputes.

Foreign minister Carl Bildt is not among the initial 40 people called answer questions about oil company Lundin Petroleum’s activities in the Sudan, as prosecutors in Sweden continued an investigation into the company's activities.

Instability in South Sudan’s oil-rich Unity state threatens the already fragile, newly independent country, the International Crisis Group has warned.

The ICG considers Unity a test case for the broad range of deferred internal issues that South Sudan has to deal with after six years of focusing on the peace deal that ended decades of civil war with the north and culminated in peaceful secession in July.

Three months after the south seceded, Sudan's economy is floundering, with rampant food inflation, lost oil revenue and costly military campaigns becoming a serious crisis for veteran president Omar Hassan al-Bashir.

An armed group belonging to Misseriya tribe opened fire on workers in a Chinese oil field in South Kordofan's Balila area on Wednesday, 28 September 2011.

China is prepared to mediate between North and South Sudan in order to bridge difference in views regarding outstanding post-secession issues, the visiting Chinese Foreign Minister Yang Jiechi said.

The Chinese foreign minister Yang Jiechi said that North and South Sudan "will lose the peace equation" by not cooperating on the joint and controversial issues.

The authorities in Port Sudan have allowed an oil shipment to leave for its destination after several days of delay over the non-payment of custom duties by South Sudan. It is unknown how much South Sudan had to pay so that Khartoum unblocks the shipment.

The Sudanese government confirmed that authorities in Port Sudan refused to allow an oil shipment to leave because of unpaid fees by the South.