Sudan says it has arrested several members of the security forces who are accused of murder, rape and burning villages in the Darfur region.
Darfur refugees accused the government of arming the Janjaweed
The Sudanese justice minister said 15 men would stand trial.
The BBC's Jonah Fisher in Sudan says it is the first time that Sudanese security personnel have been arrested over atrocities committed in Darfur.
Khartoum says it would reject any UN vote which refers war crimes suspects to the International Criminal Court.
The UN Security Council is expected to vote on Wednesday on a French-drafted resolution on whether to send suspects in Sudan to the new court in The Hague.
The pro-government Janjaweed militia in Sudan's Darfur region are accused of killing thousands of villagers and forcing two million from their homes.
A UN commission earlier this year found the atrocities committed in Darfur could be crimes against humanity, and said the culprits should be tried at the ICC - which was created to deal with cases of war crimes and genocide.
Justice Minister Ali Mohamed Osman Yassin told reporters a government committee had arrested 14 people in West Darfur and one in North Darfur state.
The committee had not yet finished work, he said.
"The objective of the commission is to investigate criminal offences," he said.
"They are going to investigate... rape crimes, human rights violations, crimes against humanity and war crimes," he added.
Darfur's rebel groups say that people are being killed while the world powers squabble over where to refer the war crimes charges.
Even though nine Security Council members are expected to support France's resolution, the outcome is still uncertain.
The US has the power to veto the move. It rejects the court, saying Americans abroad could be targeted by politically motivated prosecutions.
Nigeria had previously proposed setting up a special Africa-run tribunal in order to break the deadlock.
Russia and China, which have close ties to the Sudan government, have blocked previous attempts to threaten sanctions on Sudan if the violence does not stop.