Rebels attacked government forces in Unity State, where oil fields have been abandoned due to fighting.
25 people including civilians were killed, a local government official said on Tuesday.
The clash between rebels loyal to exiled former Deputy President Riek Machar and government forces occurred early Monday in Nhialdiu, a village close to the town of Bentiu which has changed hands repeatedly since civil war began nearly four years ago.
Those killed during Monday’s fighting in the town of NhialDiu included women, elderly people and local police officers, Lam Tungwar, state minister of information of Northern Liech state, told Reuters.
A rebel spokesman, Lam Paul Gabriel, put the death toll at 18 while the government said it had managed to repulse the rebels and were pursuing them.
South Sudan, which gained independence from Sudan in 2011 after protracted bloodshed, fell into civil war in late 2013 with troops loyal to President Salva Kiir fighting those of the ex-vice president he sacked, Riek Machar.