At least one fighter died and 18 others injured when an SPLA-North vehicle overturned Thursday evening in Heiban County of Nuba Mountains.
The vehicle was travelling from Heiban to Nyakima on a mission.First Lieutenant Nasradin Apero was among the injured.
He said their comrade died on the way to the hospital and another remains in a critical condition.
First Lieutenant Apero said the driver was over-speeding and lost control when he manoeuvred to avoid hitting a motorbike.
The vehicle rolled over three times.
The wounded fighter called on drivers to keep the law and avoid over-speeding as people can lose their lives if accidents happen.
The survivors are receiving medical treatment.
Health officials said they are responding well to medical care.