South Africa's former president Jacob Zuma, who has been in police detention since last night as he starts a 15-month prison sentence for contempt, will be eligible for parole after around four months, the justice minister said.

Zuma turned himself in to police to begin his jail term for defying a court order to attend an inquiry into corruption while he was in power from 2009 to 2018.

The ability of authorities to bring Zuma to book has been seen as a major test of the rule of law is post-Apartheid South Africa.

Zuma will be held in isolation for 14 days in line with Covid-19 protocols, Justice Minister Ronald Lamola said.

"This is not a moment of celebration or triumphalism, it isa moment of restraint and to be human," he said, promising totreat Zuma like any other inmate.

Zuma was admitted overnight to the Estcourt Correctional Centre, about 175km from his rural homestead in Nkandla in eastern South Africa.

Zuma denies there was widespread corruption and had thus far not cooperated with the legal process against him, maintaining that he was the victim of a political witch-hunt.