Khartoum - At least 15 people have been killed in clashes between two ethnic groups in the Southern Sudan state of Jonglei.

The violence followed an attack by an armed Dinka group on a settlement of Nuer Thiang tribespeople.

A military spokesman said the death toll could rise. There was no immediate information on Dinka casualties.

Earlier this month, ethnic fighting in the state - often sparked by cattle rustling and other disputes - resulted in the deaths of some 130 people.

"On the Nuer side some 15 were killed and 16 wounded," southern army spokesman Kuol Deim Kuol said of the most recent clashes, according to Reuters.

"We don't yet have details of the casualties on the Dinka side."Upcoming elections.

He said it was unclear about what sparked the fighting near the settlement of Fangak.

"It could be tribal differences. We don't know yet."

Earlier this month, the UN expressed concern at the flare-up of violence in Southern Sudan, urging the regional government to investigate the incidents during which women and children have been targeted.

Last year, some 2,500 people died in fighting between different ethnic groups in the semi-autonomous region and 350,000 fled their homes - a higher death toll than the country's western Darfur region.

The flare in violence comes ahead of presidential and legislative elections, due in April.

Southern leaders accuse northern political leaders of stoking violence in the south by arming ethnic militias to destabilise the oil-rich region.

A referendum is due next year on whether the south, one of the poorest areas of the world, should become independent.