|Southern leaders have accused the north of arming the renegades, charges Khartoum denies [Reuters]
At least 31 people have been killed in a clash between south Sudan's army and rebel militia fighters, the army said, the latest violence to unsettle the region ahead of its independence in July.
Twenty of the victims were southern army soldiers who died on Tuesday in the clash in the oil-producing Unity state with fighters loyal to Peter Gadet, a former senior southern army (SPLA) officer who rebelled this month, the military said on Wednesday.
"They (the rebels) overran a village in Mayom county. They burned it to the ground before the SPLA chased them off," Philip Aguer, a southern army spokesman, said.
Two drivers were also killed when two civilian trucks hit landmines in the same county, Aguer said, adding that the rebels fought alongside Misseriya tribesmen from the north.
Southern leaders have accused their former civil war foes in the north of arming the renegades to try and destabilise the region and keep control of its oil, charges Khartoum denies.
The Misseriya who drive their cattle south to graze during the dry season claimed sole responsibility for the attack.
"We attacked an SPLA base in ...Unity state to return 1,700 cows that the SPLA had stolen from us," said Ismail Hamadein, a senior Misseriya official.
He said 11 of his tribe died and 22 were injured during the attack on Tuesday, but said they had no links to Gadet.
Northern staff expelled
Unity authorities responded to the latest violence by expelling northern Sudanese staff working in oil-producing areas of the state, underscoring the risk from rising tensions.
"Unity State have ample evidence that these militia are being encouraged, sponsored, organised and planned by elements in the national government," Gideon Gatpan Thoar, the state's information minister, said.
Oil is the lifeblood of both economies and how to share the revenues after separation remains unresolved.
Southern oil is currently spilt roughly 50-50 with the north, and the south will still have to rely on pipelines in the north after July.
The United Nations has said more than 800 people have died in the violence in south Sudan this year stemming from tribal fighting and clashes between soldiers and at least seven bands of renegade fighters in the territory.
Analysts have warned any further deterioration could destabilise the whole region. South Sudan's neighbours include Kenya, Uganda and Ethiopia.
Renegade fighters have accused the south's government of corruption and crackdowns on opposition supporters, charges denied in the southern capital Juba.
Rights group Human Rights Watch (HRW) has accused both SPLA and rebel fighters of human rights violations during a battle in Upper Nile State in March. Aguer dismissed the allegations against the SPLA.
The south has fought the north for all but a few years since 1955 over differences in religion, ideology, ethnicity and oil.
The conflict has claimed an estimated two million lives.