Sudan's military says recent army infighting related to southern Sudan's anticipated independence has killed at least 50 people.
The latest clashes took place in two towns in the south's Upper Nile state. Officials say the fighting erupted in Melut and Paloich Saturday, after soldiers from the south refused orders to withdraw to the north.
Earlier clashes last Thursday between northern and southern soldiers occurred in the town of Malakal. The military said that fighting erupted after southern soldiers refused orders to redeploy their weapons to the north.
The new Republic of South Sudan is expected to declare formal independence in July.
Preliminary results from a January referendum show that 99 percent of southern Sudanese voted to separate from the north.
The independence vote was part of the 2005 peace deal that ended Sudan's north-south civil war.
The north and south still have to resolve issues over water, oil revenue, and the fate of the oil-producing Abyei region.
Sudan's President Omar al-Bashir has promised to accept the referendum results and has acknowledged the south voted overwhelmingly to secede.
During a speech Saturday, Bashir promised a future of freedom for his country.
He said the north would continue to be governed by Islamic Sharia law because the vast majority of northern citizens are Muslim.