S Sudan woman sees sister-in-law gang raped then killed
12 June 2014 Last updated at 08:29 BST
An international summit to discuss how to tackle sexual violence during war is under way in London.
The BBC's Karen Allen reports from South Sudan which has seen a sharp rise in the number of sexual assaults since fighting between two ethnic tribes, the Dinka and the Nuer, erupted in December.
One woman she spoke to described being forced to watch as sister-in-law was gang raped and then shot dead.