Major General Lul Ruai Koang told AFP that the fighting erupted on Saturday as security forces carried out an operation to disarm civilians in the area which has seen deadly inter-communal clashes.

More than six years after a civil war broke out in the country, and in the absence of a functioning government, many communities are flush with weapons, which they keep for protection or defense against cattle raids.

The violence in Tonj began after several armed youths got into a disagreement with soldiers. An initial armed confrontation was brought under control, but according to Koang the youths mobilised others for an attack on the army position.

"On the latest, the number of those killed, I can confirm to you that it rose to 127," said the spokesman Major General Lul Ruai Koang, adding that 45 of those killed were security forces and 82 were youths from the area.

A further 32 soldiers were injured.