The government of Sudan's semi-autonomous southern region has accused the national army of trying to provoke a new civil war.
South Sudan's information minister, Gabriel Changson Chang, made the charge Wednesday, a day after heavy fighting broke out at the key town of Malakal. Southern army troops fought with members of a militia group that was backed by the Sudanese government during the long civil war.
Chang blamed the clashes on militia leader Gabriel Tang, who returned to the town earlier this week.
But Tang told reporters in Khartoum Wednesday that he had been acting in self-defense, and denied that the government was involved. He said he went back to Malakal for a family-related visit.
Tang's militia was also involved in an outbreak of fighting in Malakal in 2006 that severely tested the peace deal that ended the civil war.
Casualty figures from the new clashes are still not clear.
Officials said the army units posted in Malakal are part of a joint force combining former rebels and pro-Khartoum government forces, and some of its soldiers are former members of Tang's militia.
The town lies near the border between northern and southern Sudan.
The 2005 peace agreement ended 21 years of civil war between Sudan's Muslim government in the north and Christian and animist rebels in the south. The war and related famines and diseases killed an estimated two million people.
United Nations officials and analysts have warned that the peace deal is still fragile and could collapse amid issues that remain unresolved, such as the position of the north-south border.
The now semi-autonomous south is scheduled to vote in 2011 on whether to secede from the rest of Sudan.
Some information for this report was provided by AFP and Reuters.