JUBA, Sudan (Reuters) - Forces loyal to a renegade south Sudanese general ambushed government troops, killing 20 soldiers and injuring 50, the southern army said Tuesday.
General George Athor rebelled after losing elections in April for the governorship of the oil-producing south's Jonglei state, raising tensions ahead of a referendum on southern independence which is due to take place next month.
South Sudan's leader Salva Kiir offered a pardon to Athor in October and both sides had agreed to keep out of each other's way until negotiations were concluded.
"George Athor's forces laid an ambush for an SPLA (southern army) company in Pigi county in Jonglei state," said southern army spokesman Philip Aguer.
"There were 20 SPLA soldiers who were killed in the clash and more than 50 were wounded." Aguer said he did not know what provoked the attack Saturday.
"You would have to ask George Athor himself. It is a very, very strange thing to do," he said.
"This happened in the middle of talks with George Athor. But this incident will be treated separately and amnesty negotiations will continue."
Athor did not answer calls to his satellite phone. The Sudan Tribune website earlier quoted Athor saying the army attacked his positions twice over the weekend.
Aguer said he did not know if any of Athor's men had died and details of the clash were still emerging from the remote area. He earlier said at least 14 people died.
"Their force scattered into the tall grass and it is impossible to know how many have been killed or injured." he said."
French oil group Total holds a largely unexplored concession in Jonglei.
Kiir said he was offering the pardon to Athor and other rebellious militia leaders to give the region a fresh start ahead of the referendum, promised under a 2005 peace deal that ended decades of civil war with the north.
Most southerners are expected to choose to separate from the north. The north-south civil war also saw fighting between rival southern clans and militias and there have been fears these could re-emerge in the uncertainty surrounding the plebiscite.
Sudan's north-south war -- Africa's longest civil conflict -- was fuelled by differences over religion, ethnicity, oil and ideology. It killed an estimated 2 million people, forced 4 million to flee and destabilised much of east Africa
Reporting by Jeremy Clarke; writing by Andrew Heavens; editing by Giles Elgood