Henry Okah, leader the Movement for the Emancipation of the Niger Delta, MEND, has accused the South African government of maltreating him.
In a statement he released after the affirmation of his conviction by a constitutional court, Okah vowed to seek redress from the International Court of Justice, ICJ, in the Hague, Netherlands.
He also described the Niger Delta agitation as similar to the Apartheid struggle embarked upon by African National Congress, ANC.
South Africa's top court had reinstated a 24-year prison sentence for Okah, convicted of a series of attacks in Warri and Abuja in 2010.
However, the MEND leader described the reinstated conviction as "laughable," accusing the court of "side-stepping critical questions raised by his legal team."
According to him, "the situation in the Niger Delta is a conflict as defined by International Human Law, IHL, the internationally-accepted body of legislation for adjudicating conflict situations.
"Therefore, prosecuting a party to a conflict in a foreign country under the South African anti-terrorism act, where the same statute is inapplicable to other parties to that same conflict is, in my opinion, illogical and, in fact, absurd.
"The South African armed struggle against apartheid, and that undertaken by the Movement for the Emancipation of the Niger Delta, MEND, are not dissimilar in substance.
"Even more shocking is the continual imprisonment as common criminals in South African prisons of soldiers of liberation armies, who had been captured by the Apartheid government almost a quarter of a century after independence in South Africa.
"I have been seriously mistreated by the South African government which had forged virtually all the documents used in my trial. I have been assaulted, electrocuted, denied sunlight and possibly poisoned in the last four years.
"For four years, I have been fed with two slices of bread for breakfast, five slices for launch, and five for dinner. Despite being seriously ill, I have been denied access to a doctor and I have been forced to live with a growth in my throat and severe abdominal pains for the last one year, but such inhuman treatment will never dampen my spirit."
He accused South Africa of using its justice system to aid foreign governments engaged in civil strife with their civilian population, calling for a united coalition across Nigeria to fight the elite he accused of plundering the nation's resources.