Unregulated large-scale land acquisition in south Sudan by foreign companies threatens the rights of the people, with an area bigger than Rwanda earmarked for use by outside businesses, a report released on Tuesday warned.

Investigations commissioned by Norwegian People’s Aid calculated that between 2007 and 2010, "foreign interests sought or acquired a total of 2.64 million hectares of land (6.52 million acres) in the agriculture, forestry and biofuel sectors alone."

"That is a larger land area than the entire country of Rwanda," said the report's author, David Kuol Mading.

If domestic investments, tourism and conservation are added, the figure rises to 5.74 million hectares (14.17 million acres), or nine percent of southern Sudan’s total land area, the report said.

South Sudan is due to gain independence in July after southerners voted almost unanimously for secession in a landmark referendum in January.

The oil-rich but grossly underdeveloped south was left in ruins by decades of war with the north, and in the transitional period ahead of independence experts say there is no clear process for large-scale land acquisition.

Many of the agreements are in name only -- and may not be recognised by the central government -- and several companies still have no visible presence on the ground.

The report acknowledges that the investments could help boost sorely needed development, but it warns that without care they could also threaten the fledgling nation.

"With the nascent state of government, a society still reeling from years of conflict, and the legal ambiguity of the transitional period, there is also a danger that this influx of investment, if left unchecked, may serve to undermine livelihoods," it added.

The largest land deal detailed in the report is the alleged leasing of 2,280,000 hectares (5,631,600 acres) in Boma National Park in Jonglei state by Emirati company Al Ain Wildlife.

The next biggest are agricultural ventures, by US firms Nile Trading and Development and Jarch Management, which have leased 600,000 hectares (1,482,000 acres) in Central Equatoria state and 400,000 hectares (988,000 acres) in oil-rich Unity state, according to the report.

The latter scheme results from a controversial deal struck two years ago between Jarch, a New York-based investment house, and former warlord turned deputy commander of the south’s army Paulino Matip.

Analysts say farmland across Africa has come under growing pressure in recent years from large-scale farming by international investors, with activists warning of the risks that it could deny residents their own resources, boosting insecurity.

Mading said the government should temporarily suspend large scale investments.

"That will allow time for the proper procedures to be put in place, so that investment can be done in a responsible manner."