A mutiny by Sudanese troops refusing to leave the south ahead of its expected independence has spread through towns in an oil-producing state, with at least 50 people killed in the past four days, officials said.
The southern and northern armies are carrying out a difficult process of splitting up and dividing their weapons, with Southern Sudan expected to emerge as Africa's newest state on July 9 following a referendum last month.
Battles with tanks and machineguns broke out in the politically sensitive southern town of Makalal on Thursday when southern members of a northern army unit refused to redeploy to the north and turned on other members of their unit.
Fighting then spread from Makalal, capital of Upper Nile state, to the settlements of Melut and Paloich on Friday and Saturday, state officials told Reuters on Sunday.
The area includes oil concessions run by Petrodar, a consortium led by CNPC of China and including Malaysia's Petronas and Sudan's own Sudapet.
Final results of last month's referendum are due to be announced on Monday. Early results show the vast majority of southern voters chose independence in the vote, the result of a 2005 peace accord that ended decades of civil war.
"The fighting in Malut yesterday (Saturday) killed 19 and wounded 18 ... In Paloich 11 were killed and eight wounded," said Akuoc Teng Diing, county commissioner of Melut county. All the dead in the two locations were soldiers, he said.
Officials earlier had said 20 people died in Malakal, including two children and a Sudanese driver working for the U.N. refugee agency UNHCR, caught in the crossfire.
Malakal has been patrolled by a combined military unit made up of the north's Sudan Armed Forces (SAF) and the south's Sudan People's Liberation Army (SPLA). The United Nations says the joint force is in the process of splitting up.
The SAF unit included many southern soldiers drawn from a militia that fought alongside the north during the civil war. Southern army spokesman Philip Aguer said it was those southern soldiers in the SAF unit who resisted the redeployment north and began exchanging fire with other members of the same SAF unit.
Aguer said one part of the unit was now heading north with the weapons, while the attackers had remained in the south.
"We know where they are. They have stopped shooting," he said. "Nobody has been arrested. How do you arrest people with guns? Negotiations are ongoing."