South Sudan’s President Salva Kiir has ordered the release of all prisoners of war and political detainees.
The move is part of a peace agreement signed last month with the rebel leader Riek Machar.
A number of Mr Machar’s fighters and supporters are in detention, along with activists and other critics of Mr Kiir’s government.
Many of the prisoners are being held in military facilities in the capital, Juba.
The aim of the peace deal is to end more than five years of civil war in South Sudan which became independent in 2011.
It states that Mr Machar should return to government as one of five vice presidents.