Evidence links a captured son of late ruler Muammar Qaddafi to recruiting mercenaries and executing people, according to the head of the International Criminal Court, Luis Moreno-Ocampa.
Moreno-Ocampa declined to disclose the nature of the evidence.
The ICC is in a tug-of-war with Libya over who should try Saif al-Islam Qaddafi, once considered his heir apparent.
He was captured last year in Libya after a civil war that toppled the Qaddafi regime.
Libya wants to try him there, but the ICC says it has jurisdiction over the case.
Human Rights Watch said on April 19 that it expects the ICC prosecutor to press Libya to hand over Saif al-Islam to the court for trial.
Based on reporting by AP