JUBA (Reuters) - At least 50 people have died as a mutiny in the Sudan army spread through towns in oil-producing Upper Nile state, stoking tension as the south prepares for independence, the military said on Sunday. Heavy fighting, with tanks and machineguns, first broke out in the politically sensitive southern town of Makalal on Thursday, when members of an army unit refused to redeploy with their weapons to the north and turned on other members of their unit. Fighting then spread from Makalal, Upper Niles capital, to the settlements of Melut and Paloich on Friday and Saturday, state officials told Reuters. The violence is a worrying accompaniment to the separation of Sudans northern and southern armies and their military hardware ahead of the southern secession, expected on July 9. Early results from a referendum in January show the vast majority of southern voters chose to separate from the north. Final results of the vote, promised in a 2005 peace accord that ended decades of civil war, are due to be announced on Monday. 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 were soldiers, he said. Officials earlier said 20 people died in Malakal, including two children and a Sudanese driver working for the UN refugee agency UNHCR, caught in the crossfire. Malakal is currently patrolled by a combined military unit made up of the norths Sudan Armed Forces (SAF) and the souths Sudan Peoples Liberation Army (SPLA), a force the UN said was in the process of splitting up before the souths independence. The situation was complicated by the fact that 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.