"Around 700 to 800 rebels launched a surprise attack on the town of Sheiria yesterday. The attack lasted an hour and they used artillery," said a senior official in the office of the armed forces spokesman.
"A number of civilians and soldiers died in the attack on the town," he told Reuters, adding it was not clear how many were killed.
Rebel officials based near the area, around 70 kilometers (45 miles) northeast of Nyala, capital of South Darfur state, said they had not heard about the attack.
Rebels at peace talks in Nigeria said on Monday militias and government forces killed 30 people in attacks in Darfur.
The African Union, the body mediating the talks, said the rebels had considered boycotting the talks but were persuaded to await the outcome of an AU investigation into the violence.
The Sudanese military official said rebels who carried out the attack on Sheiria could have been a break-away faction of the Sudan Liberation Army (SLA) aiming to disrupt the peace talks being held in Abuja.
The two main rebel groups in the area, the SLA and the Justice and Equality Movement (JEM), launched the rebellion in early 2003 complaining about marginalization from power and resources.
Fighting between the government and the rebels was reported to have died down before surging again in the run-up to the sixth round of Darfur peace talks which started in the Nigerian capital on September 15.
The fighting has killed tens of thousands of people and driven around 2 million from their homes since the start of the rebellion. Aid officials have recently said banditry has increased in the area and is disrupting aid deliveries.
The rebels say the government armed militias drawn from nomadic communities who burned and looted farming villages.