Nearly 40 aid workers have been evacuated from a northern area of South Sudan due to deteriorating security, the UN food agency says.
The World Food Programme (WFP) said 38 people from three UN agencies and three aid organisations were flown out of Jazeera and Nhialdu in Unity State last week amid signs that fighting is imminent.
Fighting erupted in South Sudan at the end of 2013 between soldiers loyal to President Salva Kiir and those backing his former deputy Riek Machar.
A peace deal signed in 2015 proved shaky and fresh clashes flared in the capital, Juba, in July, raising fears the young nation could slide back into civil war.
The conflict has helped fuel a hunger crisis, affecting an estimated 4.8 million people.
WFP said its rapid-response team had registered nearly 25,000 people for food assistance in Jazeera before being pulled out.
They have been relocated to the central town of Rumbek.
Other humanitarian staff were working on education, water, sanitation and protection programmes as well as projects to rebuild livelihoods. They were flown to Rubkona town.
"We hope the security situation will improve enough to allow re-deployment of our team as soon as possible so we can get people the food assistance they need," a WFP spokeswoman said.
The Danish Refugee Council confirmed seven of its staff working on food security and protection had been relocated and would return as soon as tensions eased.
Insecurity across South Sudan has uprooted some 1.6 million people from their homes and another one million have fled the country.
South Sudan had more attacks on aid workers than any other country last year, including shootings, rapes and mass lootings.
At least 57 aid workers have been killed since the end of 2013 and many more are missing.