Mahgoub Hussein, spokesman for the Sudanese Liberation Army, said on Wednesday that Sudanese troops backed by allied militias have targeted its strongholds at Manywashi in the west of Darfur and Teioshya in the east.
"Sudan is playing games, attacking our people and coming here for peace talks," Hussein said in the Nigerian capital of Abuja, where the talks are being hosted. "If the attacks continue, we'll not continue the talks."
It was the latest setback in the effort to bring calm to a region where war has sparked one of the world's worst humanitarian disasters. Tens of thousands of people have been killed - many from hunger and disease that have taken hold amid the chaos - and more than 2 million others have been displaced from their homes since fighting broke out more than two years ago.
A spokesman for the African Union hosting the talks, Nourddine Mezni, said the bloc's military monitors in Darfur have not confirmed any fresh attacks but said the rebels' claims will be investigated.
Government officials weren't immediately available for comment. Four previous rounds of talks failed to end the two-year conflict that has led to at least 180,000 deaths and forced around two million people from their homes.
Rebels say Sudanese troops and
militias attacked their positions
Since peace talks resumed on 10 June after a six-month break, negotiators from the 53-nation AU have largely been holding consultations with the different parties on the terms for face-to-face talks.
Wednesday's threat spells new difficulties for mediators already battling against the smaller rebel group, the Justice and Equality Movement, which objects to the presence of Chadian representatives at the talks.
The smaller rebel movement is accusing Sudan's western neighbour of supporting Sudan's army against the rebel group's forces.
In turn, Sudan's delegation wants observers from Eritrea to quit the talks and is accusing the country's government of being the main supporter of the Darfur rebels.
On Monday, Sudan said its forces had beaten off a rebel attack in eastern Sudan in which Justice and Equality Movement rebels from Darfur, took part.
The United Nations mission in Sudan said it had received reports of a rebel attack, and there were reportedly casualties on both sides.