Amnesty International has said that both South Sudan's army and rebel groups are using weapons imported from China, Ukraine and neighbouring Sudan in fighting that has claimed dozens of civilian lives.
The UK-based rights organisation released a detailed report on Thursday focusing on the clashes between the South Sudanese armed forces, known as the Sudan Peoples Liberation Army (SPLA), and the rebel South Sudan Liberation Army (SSLA) in 2010 and 2011.
Erwin van der Borght, Amnesty International's Africa director, denounced the trade in arms in the area.
"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," he said.
Helen Hughes, co-author of the report, said "the evidence that Amnesty International gathered included documenting Chinese manifactured mines that had been freshly laid on the road of Unity state".
"We've been able to, from the markings, determine that they had come from apparently a single manifacturer," she said.
Amnesty said the SPLA used Ukrainian-supplied T-72 battle tanks during the fighting.
"These battle tanks are entirely unsuitable for urban fighting as they cannot distinguish between military and civilian objects in urban areas," the group claimed in a statement.
The rebel SSLA laid Chinese-made anti-vehicle mines and were firing Sudanese-made ammunition, according to the report.
"Scores of civilians have been killed or injured in the past year due to the laying of these mines by the SSLA and this also increases food and fuel costs as the mines hamper access in the region," said Amnesty.
Speaking to Al Jazeera, Hughes said Amnesty is "calling for states to ensure that there is strong rules that will actually protect human rights and stop arms transfer where there's a substantial risk that those arms are likely to contribute to serious human rights violations".
On Monday, talks begin at the UN in New York for a new international arms trade treaty (ATT).
"The ATT talks are an unprecedented opportunity to stop arms getting into the hands of human rights abusers," said van der Borght.
South Sudan seceded from Sudan on July 9 last year but has since been wracked by internal and external conflict.
Source: Al Jazeera and agencies