The trial of a presumed militant leader accused of masterminding two deadly bombings at Nigeria's 50th independence celebrations two years ago opens Monday in South Africa, his lawyer said.

Nigerian national Henry Okah is facing trial in South Africa, where he has permanent residence, on charges that he orchestrated the twin car bombings which killed 12 people in Abuja on October 1, 2010.

Okah, the presumed leader of the Movement for the Emancipation of the Niger Delta (MEND), also faces terrorism charges over two explosions in March 2010 in the southern Nigerian city of Warri, a major hub of the oil-rich Delta region.

"It's Okah's first day of trial in the South Gauteng High Court today. The defence and prosecution teams are ready to proceed with the matter and a judge has been allocated," his lawyer Tsietsi Majang told AFP.

The case was last in court in January when lawyers had asked for more time to prepare their arguments.

South Africa is trying Okah as part of its international obligations because Nigerian authorities have not applied for his extradition, according to the prosecution.

Okah has denied involvement in the attacks, which were claimed by MEND, and also denies being the leader of the group which is fighting for a greater share of the Delta region's oil wealth.