Okah appeared at the South Gauteng High Court on Monday over his alleged involvement in deadly bomb blasts
during Nigeria's 50th independence anniversary celebrations.
More than 10 people were killed and many others were injured in the bomb blasts on October 1, 2010.
Okah was arrested in Johannesburg a day after the bombing in Abuja.
According to the prosecution, the South African government has put Okah on trial to honour its international obligations after Nigerian authorities did not apply for his extradition.
Okah was said to be the leader of the Movement for the Emancipation of the Niger Delta (MEND), a group which has been fighting for a greater share of Nigeria's oil wealth, and claimed responsibility for the blasts.
Security experts believe Okah - who accepted a government amnesty last year after gun-running and treason
charges against him were dropped - was at one time the brains behind MEND, although he has denied ever being its leader.