Sudan's main rebel group has accused the Sudanese government of violating a cease-fire agreement the two signed in 2002. The rebels say this could scuttle the Sudanese peace talks.
The spokesman for the Sudan People's Liberation Army, Samson Kwaje, told VOA a recent battle in western Upper Nile is the latest violation of the cease-fire the two sides pledged to uphold during their negotiations.
More than 50 people were reportedly killed in clashes last week in Tonga, a town near the state capital of Malakal, the U.N. news agency IRIN reported.
According to Mr. Kwaje, Sudanese government forces shelled Tonga in an attempt to evict rebel troops from their base. The next day, he says, the rebels regrouped and drove the government's forces out, killing two government soldiers.
But Sudan's deputy ambassador in Nairobi, Dirdeiry Ahmed, says no Sudanese government troops were involved in the Tonga fighting. "We are having many militias affiliated with either party, with either the government or the SPLA, so those are the ones involved," he said.
Independent news from the Tonga fighting was hard to come by.
The Kenyan mediator of the Sudanese peace talks, retired General Lazaro Sumbeiywo, says the seven-nation regional grouping that sponsors the peace talks will investigate.
"These [militias] are groups that move from one side to another," explained Gen. Sumbeiywo. "One group jumps to one side, and starts claiming an area where there have been the other side. So, it starts being a problem. But we are investigating."
The peace talks between the SPLA rebels and the government have been taking place in Kenya for about a year and a half.
General Sumbeiywo says the Tonga battle will not disrupt the peace talks.
But rebel spokesman Mr. Kwaje disagrees. He said the Tonga battle was the latest in a string of violations, and it may well affect the outcome of the talks.
"Why should the government violate the cessation of hostilities [agreement], not only there, but they have been even attacking some parts of central Upper Nile. So, the government is out to maybe scuttle the peace talks," he said.
Government spokesman Mr. Dirdeiry has said the government is firmly committed to the peace process.
The peace talks aim to end more than 20 years of civil war between the government and rebels that has claimed two million lives.