The United Nations children agency says up to 250 child soldiers including four girls were released yesterday in Jonglei state from the Cobra Faction.
UNICEF says another 400 hundred will be released in two days.
This is the third release of children following a peace deal between the faction and the Government.
660 children were released last month in Pibor and Gumrok.
UNICEF Representative in South Sudan, Jonathan Veitch says 200 of the child soldiers have already been re-united with their families.