A deadly firefight on Monday killed at least 25 people after Sudanese security forces thrust into one of the largest camps for displaced people in Darfur, witnesses and rebels said.
Reports of casualties varied wildly and there was no immediate confirmation of numbers from aid workers or UN officials compiling their own statistics.
The violence came just hours before Djibril Bassole, the new international mediator trying to find a political solution to end five years of war in Sudan's western region of Darfur, was to arrive to take up his post.
Witnesses said government forces massed at dawn outside Kalma, a highly charged camp in South Darfur that is home to up to 100,000 people displaced by the conflict and which the authorities have previously wanted to empty.
Adam Mohamed, a community leader in Kalma, said 30 people were killed and 25 wounded in clashes with police before the heavy gunfire subsided.
"The government forces still surround the camp. There is no fighting now but tension is high throughout the camp and no one knows where the wounded people have been taken," Mohamed told AFP by telephone.
"This morning security forces surrounded Kalma camp and demanded that every IDP (internally displaced person) leave," said Ahmed Abdel Shafie, a commander in the nebulous rebel Sudan Liberation Army (SLA), from elsehwere in Darfur.
"Later, they opened fire on the eastern side of the camp. There were many casualties. Up to now, we have 27 confirmed dead and 75 wounded.