Sudanese government troops clashed with units made up of soldiers from the south in the city of Malakal in Upper Nile state, killing at least six people and wounding 22, a state government spokesman said.

The fighting started last night when southern soldiers in the Sudanese government army refused orders to move to northern Sudan out of fear they would be disarmed, Bartholomew Pakwan Abwol, the state director general of information, said today by phone from Malakal. Upper Nile is one of 10 states in Southern Sudan.

�No one has gone to the scene of the fighting,� he said. �Everyone is very scared. The situation is still very tense.� At least four civilians, including two children, and two soldiers were killed in the clashes, which ended at 11:30 a.m. local time, Abwol said.

Oil-rich Southern Sudan voted last month to secede from Sudan in a referendum, according to preliminary results published by the commission that organized the vote. Southern Sudan is set to become independent in July.

�We don�t have any business with these quarrels,� Philip Aguer, a spokesman for Southern Sudan�s army, said today by phone from Juba, the regional capital.

The referendum was the centerpiece of a 2005 peace accord that ended a civil war which lasted almost 50 years, except for a cease-fire from 1972 to 1983, between the Muslim north and the south, where Christianity and traditional religions dominate. About 2 million people died in the second phase of the conflict.

To contact the reporter on this story: Matt Richmond in Juba via Johannesburg at +27- [email protected].