1,340 people died from malaria in an "unprecedented" outbreak across South Sudan last year, the UN's office for coordination of humanitarian affairs (OCHA) said Monday.

There were 2.28 million malaria cases in South Sudan in 2015, a sharp increase from 1.54 million cases with 718 deaths in 2014, OCHA reported.

A third of the reported cases and three quarters of the deaths last year were among children under five years of age. OCHA said there were shortages of malaria drugs and diagnostic tests in several parts of South Sudan.

A malaria task force formed in October 2015 and distributed mosquito nets and helped identify and treat those afflicted, OCHA said. Most malaria cases occurred in the second half of the year during the rainy season.

Separately, aid workers have been providing assistance to war-affected people in Leer county in southern Unity state since December including food aid, OCHA said.

Relief agencies have treated more than 2,300 children under age 5 for severe acute malnutrition and more than 3,500 for moderate acute malnutrition, according to the group.

Leer county was one of three counties where 40,000 people were said to be in phase 5 "catastrophe," the worst level of food security possible, in October last year.

However, a famine was not declared. OCHA has not provided any information on how many people died of malnutrition in South Sudan in 2015.

Photo courtesy MSF