The International Committee of the Red Cross said it distributed subsistence assistance to an estimated 12,000 people in Jonglei, the largest state in South Sudan.
The ICRC said regional conflicts have forced many civilians from their homes, where fleeing means they're abandoning a way of survival.
"The upheaval this causes for the people displaced and for the communities that host them is massive," ICRC regional director Melker Mabeck said. "Access to land has been severely affected, while food prices have shot up, making it difficult for people to buy what they need to survive."
Sudan and South Sudan agreed recently to pull military forces away from the shared border and establish a demilitarized zone. Border insecurity has threatened the peace deal that secured South Sudan's independence in 2011.
The ICRC treated more than 60 people for conflict-related injuries in Jonglei last week. U.N. officials said violence in Jonglei is a "major concern" for the U.N. Mission in South Sudan.