Sources close to the court in The Hague told the Dutch news agency ANP on Monday that the court had decided to launch an investigation into the crisis in Darfur, where more than two million people have fled their homes and tens of thousands have been killed in fighting.
A spokesman for ICC chief prosecutor Luis Moreno-Ocampo declined to comment on the report.
The UN Security Council voted earlier this year to refer the situation in Darfur to the ICC, the world's first permanent global criminal court established in 2002 to try cases of genocide and major human rights violations.
The Darfur case is the first the Security Council has referred to the ICC, which is already investigating crimes in Uganda and the Democratic Republic of Congo.
In April, UN Secretary-General Kofi Annan gave the ICC a list of 51 people suspected of slaughter, rape and pillage in Darfur.
UN Security Council voted to refer
the Darfur situation to the ICC
They include top Sudanese government and army officials, militia leaders and rebel and foreign army commanders.
Sudan says it would refuse to hand over its citizens for trial abroad, saying it will prosecute suspects itself.
The ICC is supported by almost 100 countries but opposed by the United States, which fears politically motivated prosecutions of its soldiers and citizens.
Washington abstained from the Security Council vote on Darfur after winning guarantees that its citizens in Sudan would be exempt from prosecution by the ICC.
The United Nations says Sudan has done little to disarm the Janjawid militia accused of a widespread rape, killing and burning of villages in Darfur during a two-year rebel uprising.