UNICEF says it is shocked by the senseless killing of staff belonging to Grassroots Empowerment and Development Organization or GREDO.
The humanitarian workers were travelling in a car that was clearly marked as belonging to a NGO, it points out.
UNICEF in a statement says it is horrified that humanitarian staff working to improve lives of the vulnerable people in South Sudan were brutally targeted.
It calls on the authorities to find and hold accountable those responsible for the killing.
UNICEF conveys its deepest condolences to families and colleagues of the deceased aid workers.
GREDO is working on community-based reintegration programmes, supporting children released from armed forces and groups.