South Sudanese are surviving on tree leaves as a deadly famine declared in the East African country continues to spread nationwide, a humanitarian aid group said Monday.

The Norwegian Refugee Council (NRC) in its report said the communities it visited in South Sudan have resorted to extreme famine coping techniques such as eating tree leaves as wild fruits run out.

The humanitarian aid group notes that people are eating tree leaves even in areas where famine is yet to be declared.

"The bitter leaves eaten by families we spoke to are from the Lalop tree, and have limited nutritional value. When families eat these leaves and little else, malnutrition quickly follows," NRC's Country Director in South Sudan Rehana Zawar said in a statement.

47-year-old Bhakita Abuk (mother of seven), a resident of Amothic village, said: "Children are eating leaves off the trees, Children are suffering because there is not enough food to eat. Some of the children have diarrhea from eating the leaves," she said.

NRC warns the situation is getting worse and calls on more funding to South Sudan to help cushion the effects of the famine.

"International donors need to provide more funding for emergency aid for South Sudan to stop the famine and food crisis escalating," Zawar said.

NRC said the aid appeal for South Sudan requires $1.6 billion to support people in need. So far only 18 percent of the appeal has been funded.

Analysts argue that South Sudanese leaders are forcing famine on their people by waging violent war and conflict leaving millions at risk.

Thousands have died and more than 1.6 million people in South Sudan have been displaced since the conflict started in December 2013.