At least nine people were killed in fresh clashes in Amadi State in South Sudan's Western Equatoria, officials said.
The weekend clashes pitted the National Salvation Front (NAS) led by Gen Thomas Cirillo, and a faction of the Dr Riek Machar-led SPLM-IO.
The fighting happened at the Kediba locality, controlled by Gen Cirilo, according to the Amadi State deputy governor, Mr Manasseh Dobuyi.
The Eye radio in Juba on Tuesday quoted Mr Dobuyi saying SPLM-IO had found seven bodies, including those of two civilians.
The deputy governor further disclosed that the situation was still tense in the area, forcing civilians to flee their homes for safety.
"Civilians moved out and left the place to the National Salvation Front," he added.
Last week, the peace monitoring agency, the Revitalised Joint Monitoring and Evaluation Commission (RJMEC), expressed deep concern over the troops build-up in Yei River State.
The agency said both the government and the rebels under Gen Cirilo were deploying their forces in a move that could spark fresh fighting in the war-ravaged area.
Gen Cirillo's NAS refused to sign the September peace deal, which brought together President Salva Kiir and former rebel chief Machar in Addis Ababa.