Amnesty said Thursday scores of people have been killed or injured, seen their homes destroyed or been forced to flee because of indiscriminate attacks on civilians by the Sudan People's Liberation Army and the opposition South Sudan Liberation Army in Mayom County in South Sudan's Unity State in 2010 and 2011.
"Governments must immediately stop supplying South Sudan with conventional arms, which have been used to commit violations of international humanitarian and human rights law, until adequate systems of training and accountability are in place," Erwin van der Borght, Amnesty International's Africa director, said in a news release.
The report comes ahead of the one-year anniversary in July of South Sudan's gaining independence under terms of a peace agreement reached with Sudan in 2005 and days before world governments gather at the United Nations for Arms Trade Treaty negotiations.
Amnesty called in the release for a "strong and robust treaty with rules to end irresponsible arms transfers to those likely to use them for serious violations of human rights and war crimes."
The human rights group said an effective treaty would require all governments to stop international transfer of arms when there is a "substantial risk those arms are likely to be used to commit serious human rights violations."
"The ATT talks are an unprecedented opportunity to stop arms getting into the hands of human rights abusers," van der Borght said. "A strong treaty could help prevent many other communities suffering from the horrific cost of the irresponsible arms trade, in the way the people of Mayom County have."