The soldiers were killed in an ambush carried out by "unidentified gunmen," UNMISS said in a statement.
Seven people, including two civilians, were injured in the attack in Jonglei state.
South Sudan's military has demanded that the UN, the International Committee of the Red Cross and aid organizations leave Jonglei in the eastern part of the country, where fighting intensified in late 2025.
UNMISS does not state the nationalities of the killed soldiers.
