The International Committee of the Red Cross said more than 60 people were treated following clashes in Jonglei in South Sudan. About half of those injured required emergency surgery.
Melker Mabeck, head of the ICRC delegation in Juba, said aid workers were having trouble reaching remote areas of Jonglei.
"Fighting is ongoing and all those wounded are entitled to receive medical care," he said. "With the onset of the rainy season, reaching the wounded will become increasingly difficult."
The aid group said this is the second time in a month that it sent a surgical team to the state from Juba to respond to weapons-related injuries.
South Sudan and Sudan signed an agreement recently to set up a demilitarized zone along the border. South Sudan gained independence from Sudan in 2011 under the terms of a comprehensive peace agreement that ended the country's civil war.
Border conflicts, southern rebellions and disputes over oil have threatened the peace.