The tension around Akobo is between two subgroups of the Nuer ethnic group - who predominantly live in Sudan but also have significant numbers in Gambella - the Lou Nuer and the Jikany Nuer.
A study released on Monday by the Geneva-based Small Arms Survey concludes that despite efforts by the Southern Sudanese military to disarm Nuer-dominated militia, loosely known as the 'White Army' in southeastern Sudan, "the pacification of South Sudan has brought the social crises within Lou and other peoples increasingly to the fore".
The two pastoralist Nuer groups have frequently clashed over land, cattle, water and grazing, but in the 1990s were also caught up in opposing southern factions during the Sudan civil war.
A dialogue between the communities is being planned with of PACT International - an NGO with a background in local peace initiatives in the region.
"The Lou and Jikany have had conflicts for a long time over grazing land and access to water points," Julie Brethfeld of PACT Sudan said. While inter-clan fighting between the two had subsided, there were concerns that with potentially large increases in population and cattle, border conflicts may again arise.
Apart from tensions between the Nuer groups, both have complained to local authorties of raids by the Murle ethnic group, which lives to the west.
The Lou Nuer, say humanitarian sources, crossed into Ethiopia several years ago to avoid conflict in Sudan and access more land in Ethiopia, and in the process pushed Jikany off some of their traditional land.
According to aid workers, hundreds of Lou Nuer originally from Sudan are moving from western Gambella into southern Sudan, as the Jikany Nuer take back the land the Lou are vacating.
Planning for 5,000 returnees
Aid agencies based in Southern Sudan are preparing to assist the Lou returnees once they cross into Sudan, according to a Juba-based official familiar with the situation, who told IRIN: "Our immediate response is to provide enough assistance for 5,000 people. This includes enough food for three months and non-food items."
Some 700 returnees have been registered after crossing the border since May, but humanitarian sources say the number of Lou Nuer who may return to Sudan could top 20,000.
According to OCHA, the ongoing movements of displaced Jikany Nuer from Itang to Akobo and other areas in western Gambella were of concern. "Latent tensions remain," OCHA Ethiopia reported in its humanitarian bulletin of 11 June.
"There's a lack of water, of boreholes," Brethfeld added. Other aid sources said the health situation could deteriorate should diseases such as diarrhoea and malaria escalate.
Brethfeld said discussions about the move out of the area by the Lou Nuer had been ongoing for about a year, but the timing was questionable. "They have already begun to cultivate their fields in Tiergol and they have their shelter there," she added.
It might be too late to begin cultivation again when they resettle in Southern Sudan and that materials for building shelter are harder to find at this time of year, Brethfeld explained. The the same problems could be faced by the Ethiopian Jikany when they moved into areas vacated by the Lou.