South African authorities may launch a murder inquiry involving Winnie Madikizela-Mandela, the ex-wife of former president Nelson Mandela, after police exhumed the remains on Tuesday of two anti-apartheid activists who disappeared 24 years ago.

Corlett "Lolo" Sono, 21, and 19-year-old Siboniso Anthony Shabalala, were among about 21,000 people killed in political violence during apartheid by agents of the White-minority regime or by fellow activists within Black liberation groups.

In 1997, Sono's father told South Africa's Truth and Reconciliation Commission (TRC), a body set up to investigate apartheid-era atrocities, that he last saw his son in a pick-up truck with Madikizela-Mandela.

He told the commission Sono had been beaten up and that Madikizela-Mandela told him that his son was an apartheid spy.

In her testimony to the TRC, Madikizela-Mandela described the allegations as "ridiculous" and "lunacy", and the judge dismissed the statement from Sono's father, who is now dead.