Congolese warlord Germain Katanga has appeared before the International Criminal Court in the Hague - only the second suspect to do so.
Mr Katanga - known as Simba - was arrested two years ago
Mr Katanga is accused of murder, sexual enslavement and forcing children to fight as soldiers in the Ituri region of the Democratic Republic of Congo.
The Forces for Patriotic Resistance (FRPI) leader is the second Congolese warlord to be sent to The Hague.
Thomas Lubanga was flown there in 2006, accused of recruiting child soldiers.
War crimes charges
Mr Katanga, 29, was told of the accusations against him and his rights in detention during the procedural hearing.
Prosecutors say Mr Katanga - known as Simba - led the FRPI in north-eastern DR Congo in 2003. He was arrested two years ago.
Judges say there are reasonable grounds to believe that Mr Katanga led an attack on the village of Bogoro in which 200 civilians were killed.
The prosecution alleges his fighters, which had the support of the Lendu ethnic group, committed atrocities against civilians of the Hema ethnic group in the Ituri region.
Fighting in the gold-rich Ituri region broke out in 1999 and continued until 2003.
The war, which began as a struggle for control of land and resources, deteriorated as arms proliferated and members of the Ugandan army became involved.
This turned a local dispute into an inter-ethnic war that killed an estimated 50,000 people and left hundreds of thousands homeless.