UNICEF South Sudan spokesman Timothy Irwin told Xinhua in Juba that malnutrition rates among children are a significant concern.
"So far this year, UNICEF has admitted and treated nearly 160,000 children under five for severe malnutrition. That figure represents a 60 percent increase in admissions compared to 2015 and a rise of more than 160 percent since 2014," Irwin said.
He attributed the increase to violence spreading from Upper Nile region to hitherto peaceful areas of Equatoria regions Yei, Magwi and Wau.
"We have revised our target for the number of children we aim to treat in 2016 from 166,222 at the beginning of the year to 253,605. We have also scaled up our response in Northern Bahr el Ghazal where more than a third of the population is malnourished. Malaria is this primary cause of illness and deaths among children under five," he added.
The UN refugee agency estimates more than 100,000 people are trapped in Yei alone amid fighting between Sudan Peoples Liberation Army-In Opposition (SPLA-IO) led by the ousted First Vice President Riek Machar and troops loyal to President Salva Kiir.
Irwin urged all warring parties to adhere to international human rights and humanitarian law and ensure that civilians particularly children are protected from harm.
UNICEF is responding to high levels of childhood malnutrition through therapeutic feeding programs and carrying out malaria screening and treatment among children and their mothers.
He also added they continue to respond to a cholera outbreak in South Sudan.
South Sudan descended into civil war in December, 2013 after President Salva Kiir accused his sacked deputy Riek Machar of plotting a coup which the latter denied but formed the rebel force SPLA-IO leading to violence that killed tens of thousands and uprooted more than 2 million from their homes.
A fragile peace deal signed August last year to end more than two years of conflict was thrown in disarray after Machar who has been replaced as First Vice President by Taban Deng fled the capital Juba in the wake of renewed clash in July between the warring factions.