The prosecutor of the International Criminal Court on Friday said she would seek a full investigation into possible war crimes and crimes against humanity allegedly committed during Nigeria's conflict with the Islamist rebel group Boko Haram.

Fatou Bensouda said in a statement her office had completed a preliminary examination and found a "reasonable basis to believe" that Boko Haram and its splinter groups had committed war crimes and crimes against humanity, through murder, rape, sexual slavery, and torture. Judges must approve the request.

Bensouda's office has been reviewing the conflict between government forces and Boko Haram and its various splinter groups in western and northern Nigeria since 2010.

She said the office recognised that the vast majority of the crimes were attributable to non-state actors, but that it had also found a "reasonable basis" to believe that members of the Nigerian security forces had also committed crimes,

Bensouda's statement added that the court, set up in 2002 in The Hague, Netherlands, to prosecute atrocities when member states were unwilling or unable to do so themselves, was facing capacity constraints.

Bensouda's office in running investigations in Democratic Republic of the Congo, Uganda, Sudan, Central African Republic, Kenya, Libya, Ivory Coast, Mali, Georgia, Bangladesh and Afghanistan, and a decision on whether to investigate alleged atrocities in the Palestinian territories is pending.

Bensouda's term is due to end June 15 and her successor has not yet been chosen.