The Justice and Equality Movement (Jem) fighters were armed with rocket-propelled grenades and AK-47s.
A Jem spokesman told the BBC his group had permission from the authorities to enter the camp near Sudan’s border for supplies and to get vehicles fixed.
Aid workers say their presence in the camp, near the town of Bahay, is putting refugees’ safety at risk.
The BBC’s Celeste Hicks in Bahay says last month planes bombed three kilometres away from the camp, in what was believed to be Sudanese retaliation for Jem taking the Darfuri towns of Kornoi and Um Baru in May.
Two local people and many animals were killed.
“All the children had gone to the wadi [dry river bed] to collect firewood,” refugee Izadine Kashir told the BBC
“We heard the bombing and saw huge clouds of smoke. Everyone panicked and the women went running out of the camp to get the children.”
More than two million people have been forced from their homes during the six-year conflict in Darfur. Some 250,000 have crossed the border into Chad.
SOURCED FROM BBC