The aid agency said it has launched its own investigation into the incident.
"We detained them and military intelligence was interrogating the Sudanese staff … asking how relief vehicles are being used to help elements that are hostile to GOSS (the government of south Sudan)”, SPLA spokesman Kuol Diem Kuol was quoted as saying. He calls reports of beating as "a concoction".
In 2009, the former Sudanese foreign minister, quitted South Sudan’s ruling party, accused it of corruption, lack of equality, among others.
SPLM has denied all charges and said Akol was too close to the enemy – a direct reference to NCP.
A senior humanitarian official in Juba, who asked not to be named, said “the men were beaten”, Reuters reported.
The 2005 North-South peace agreement granted the South to keep its own army. It also allows the Government of Southern Sudan (GoSS) to transform SPLA into professional army.