Attacks against aid workers in South Sudan are worsening hunger in the war-torn state, the World Food Programme said Wednesday, as it expressed "grave concern" for four missing staff members.
The UN's WFP said it was suspending food aid deliveries to parts of northeastern Upper Nile state, scene of some of heaviest recent fighting, as it was too dangerous to send its staff in.
At least 10 aid workers have been confirmed killed in the oil-producing state since civil war broke out 16 months ago, according to the UN.
"We cannot do our life saving work unless national and local authorities are willing and able to safeguard humanitarian staff," WFP said in a statement, announcing the suspension of aid to Upper Nile's Akoka and Fashoda counties.
Three WFP workers disappeared on April 1 when they were caught up in fighting as they drove a food aid convoy, while a fourth was abducted at gunpoint from the state capital Malakal on October 2014.
"The disappearance comes amid generally deteriorating security and increasing harassment of humanitarian workers throughout the country," WFP said.
"Worsening insecurity in some parts of South Sudan will make it harder for humanitarian agencies to reach conflict-affected communities with badly needed assistance, just as the lean season is set to begin," it added.
Heavy fighting broke out Wednesday in Malakal between rival government factions.
"We are equally concerned about the welfare of innocent people, particularly women and children, who are suffering the consequences of this conflict," WFP added.
South Sudan's civil war started in December 2013 when President Salva Kiir accused Riek Machar, who had been sacked as vice president, of attempting a coup.
The UN estimates that 2.5 million people are in a state of emergency or crisis, steps just short of famine.