South Sudan's army has denied that its soldiers have killed and tortured members of the minority Murle community during a disarmament campaign.
"That is not true, that is a lie," army spokesman Col Philip Aguer told the BBC in response to the allegations made by aid workers and community leaders.
The disarmament of rival cattle-herding groups in Jonglei state began in March.
Over the last year, more than 1,000 people have died in violence between the Murle and Lou Nuer communities.
Ten of thousands of people have also been displaced in Jonglei state in the two outbreaks of clashes linked to cattle raids - one last August by the Murle and another revenge attack by the Lou Nuer in January.
South Sudan, which gained independence from Sudan last July, is awash with small arms after decades of civil war that ended in 2005.
Cattle lie at the heart of life for many communities in the country which has hardly any banks - they represent wealth, a dowry, property and a source of food in the lean season. A single cow can be worth hundreds of dollars depending on its colouring.