Foreign weapons 'fuelling South Sudan conflict'
Weapons from China, Ukraine and Sudan are fuelling conflict in South Sudan, according to Amnesty International.
It says scores have been killed and injured in indiscriminate attacks on civilian areas by both a rebel group and the South Sudanese army.
The group says a "ready flow of weapons" includes Sudanese weapons, Chinese landmines and Ukrainian tanks.
There has been no official reaction from any of the countries to the allegations.
The tanks - used by the South Sudanese army, according to Amnesty - were clandestinely delivered to the SPLA between 2007 and 2009 via Kenya, as part of a transfer involving Ukrainian, German and UK firms, the report says.
"This delivery took place despite the 2005 Comprehensive Peace Agreement between Sudan and South Sudan's ruling Sudan People's Liberation Movement (SPLM), and an EU embargo on Sudan which at the time also covered South Sudan," the group said in its report.
The report focuses on conflict in Mayom County, in the western part of Unity State.
It says that the use of "unguided, indirect-fire mortar and artillery shells" to bombard military targets "failed to discriminate adequately between civilians and military targets", in violation of international humanitarian law.
The group is urging governments around the world to stop selling weapons to countries where there is a "substantial risk" that they could be used to commit human rights abuses.
The BBC's James Copnall, in Khartoum, says that the detail of the report is likely to prove controversial though another organisation, Small Arms Survey, has come to similar conclusions in the recent past about the origins of the weapons.
South Sudan gained independence from Sudan last July, after a long civil war. South Sudan ended up with most of the area's oil fields, although it has to export the oil using pipelines through ports in Khartoum's territory.