At least 17,000 child soldiers have been recruited in South Sudan since the outbreak of the civil war in 2013, Unicef has said.
The UN children's agency said both the government and the rebel groups were guilty of recruiting the child soldiers.
“Since the first day of this conflict, children have been the ones most devastatingly affected by the violations.
“Now, as the fighting intensifies – and despite repeated pledges by all to end child recruitment – children are once again being targeted,” Unicef Regional Director for Eastern and Southern Africa Leila Gharagozloo-Pakkala said Thursday.
The UN has since last month documented at least 50 children who were abducted and recruited in the Greater Upper Nile, with unverified reports that an additional 50 others may have been recruited in the Greater Bahr el Ghazal.
The agency said it had also received reports of grave violations against children committed in the Greater Equatoria. However, due to high insecurity and restricted access, it had not been possible to verify those reports.
A total of 1,932 children have been released by the government and the rebel armed groups, 1,755 in 2015 and 177 this year, Unicef said.
The two largest parties to the conflict; SPLA and SPLA in Opposition - have both signed agreements with the UN to end and prevent the recruitment and the use of child soldiers.
Unicef and partners have since 2013 documented at least 2,342 children killed or maimed, 3,090 others abducted and another 1,130 others sexually assaulted.
According to the agencies, some 303 incidents of attacks on or military use of schools or hospitals have also been reported since 2013.
The ongoing insecurity, combined with an economic crisis that has pushed the South Sudan inflation above 800 per cent, has also created widespread food insecurity, with malnutrition among children reaching emergency levels in most parts.
This year alone, Unicef said, it had admitted 184,000 children for treatment of severe malnutrition. The figure is 50 per cent higher than the number treated last year and an increase of 135 per cent above 2014's.
“Unicef's concern is that with the prospect of increased hostilities and atrocities, the suffering that children have endured will have no end,” Ms Gharagozol-Pakkala said.
“The children of South Sudan must no longer live under constant fear of hunger or conflict. They need sustained peace, care and support,”
The UN Convention on child rights criminalises the recruitment of children as soldiers.