The International Criminal Court's prosecutor says she needs more time to build the case against against a Ugandan rebel commander who faces charges of war crimes and crimes against humanity.

Fatou Bensouda told reporters in the Ugandan capital, Kampala, on Friday that the evidence against Dominic Ongwen is incomplete and that she has requested a three-month extension of proceedings to confirm charges.

The court had previously said confirmation hearings against Ongwen — who was transferred to The Hague last month — would happen in August.

Bensouda said the extension is necessary "in light of the many years that have passed" since Ongwen's indictment.

Bensouda said she is visiting Uganda to "reestablish contacts" with Ugandans who may be witnesses in the case.