Mr Nyanda takes over from General Georg Meiring, who resigned last month over his links with a discredited report alleging a coup plot against President Nelson Mandela.

The South African security forces' first black leader, Mr Nyanda takes over at a time when the army, inherited from the old regime and still dominated by whites in the upper ranks, is under political pressure to reflect the democratic order in South Africa.

Almost 30,000 soldiers who fought in the armed struggle against apartheid have applied to join the South African army since the country's first democratic elections four years ago.

But budget pressures and the relatively stable situation in Southern Africa mean that the forces have cut their numbers from 73,000 to 50,000.

Step towards integration

The South African military is battling to overcome its racially divided past

The BBC Southern Africa correspondent says the promotion of General Nyanda, 48, is seen as a major step towards integrating senior black officers in the ranks of the country's armed forces.

General Nyanda recently paid tribute to his predecessor, acknowledging "the immense contribution he has made in the peaceful transition from the old order to the new, and in building a new defence force out of its disparate, adversarial constituent parts."

General Nyanda served as chief of staff of the African National Congress's military wing, Umkhonto we Sizwe, from 1992. After the election of the ANC to government he became chief of staff of the SANDF in 1994, and deputy chief of the SANDF in 1997.

Schooled in Soweto and expelled from the University of Zululand for his political activities, Mr Nyanda became active in the ANC underground in the 1970s.