Former Congolese militia leader Mathieu Ngudjolo Chui has been acquitted by the International Criminal Court of war crimes and crimes against humanity at the Hague.
The judge ordered his immediate release.
The case related to the killing of 200 residents of Bogoro village in Ituri province in the Democratic Republic of Congo in 2003.
The former warlord was accused of ordering the attack.
The court heard how victims were burned alive, babies smashed against walls and women raped then murdered.
Prosecutors claimed Ngudjolo sent child soldiers to carry out the atrocities.
The judge, Bruno Cotte, said the prosecution had failed to prove any connection between Ngudjolo and the massacre.
The prosecutors said that they are to appeal the decision and called for Ngudjolo to remain in custody.