Some 100 government trucks surrounded the Kalma camp, home to some 90,000 people who have fled their homes in Darfur, a rebel spokesman told the BBC.
There is no independent confirmation of the reports but international sources have been told that Sudan wants to disarm the camp's residents.
More than two million people have fled five years of conflict in Darfur.
Ahmed Abdel Shafie, who heads a faction of the rebel Sudan Liberation Army, told the BBC that the government wants to force people to leave the camp."
Another rebel leader puts the number of those killed higher. Abdel Wahed Mohamed al-Nur, said that 50 people had been killed.
"This really is a catastrophe. People are being killed while the world just watches," he said.