Security forces threw a cordon around the High Court in the southeastern city of Pietermaritzburg, the capital of Zuma’s home region of KwaZulu-Natal, where loyalists have previously gathered in rowdy shows of support.
The measures were later eased to allow street access after the area was deserted.
Zuma, 79, faces 16 charges of fraud, graft, and racketeering related to the 1999 purchase of fighter jets, patrol boats, and equipment from five European arms firms when he was deputy president.
He is accused of taking bribes from one of the firms, French defence giant Thales, which has been charged with corruption and money laundering.
The trial started in May after numerous postponements and delays, as Zuma’s legal team battled to have the charges dropped.
An emotionless Zuma made a virtual appearance from prison in the nearby town of Estcourt, sitting on a black office chair in a white-walled room, clad in a black suit, white shirt, and red tie.
He had proclaimed his innocence when he appeared in person for the opening in May. Thales has also pleaded not guilty.
On June 29, Zuma was separately found guilty of contempt of South Africa’s top court for snubbing graft investigators probing his time as president. He was jailed on July 8.
South Africa was then plunged into chaos, with looting and rioting erupting in KwaZulu-Natal, before spreading to the economic hub of Johannesburg in Gauteng province, claiming more than 200 lives.
The unrest was widely seen as at least partially in response to Zuma’s imprisonment.
The trial is resuming virtually to avoid more “disruption”, the National Prosecuting Authority told AFP, although other court cases are also being heard online due to the pandemic.
But Zuma’s legal team claims the online format is unconstitutional and has applied for the trial to be adjourned.
His lawyer Dali Mpofu argued Zuma was being denied the right to a “public trial in front of an ordinary court”, to be physically present and consult his defence.
He said the unrest was “unforeseen” and asked Judge Piet Koen to push back proceedings by “two or three weeks.”
Zuma’s legal team has meanwhile also demanded that chief prosecutor Billy Downer recuse himself from the case over claims he leaked information to the media.
Downer has accused them of delaying tactics, which Mpofu vehemently denied.
Monday’s hearing could reignite tensions that had eased by the weekend, analysts warn.
The charismatic ex-leader has retained a fervent support base within the ruling African National Congress (ANC) party and among the general public.
His followers portray him as a man of the people and a defender of the poor.
“People will be watching the behaviour of judges,” said Sipho Seepe, a fellow of the University of Zululand in KwaZulu-Natal.
“If they feel justice is not done, they will protest.”
Zuma and his backers have repeatedly dismissed the scrutiny of the ex-president’s conduct as politically motivated and warned his jailing would spark unrest.
But they deny being behind the recent turmoil.
Zuma once dubbed the “Teflon president”, has started serving a 15-month jail sentence for contempt.
He was arrested for disobeying a Constitutional Court order to testify before a judicial panel probing the plunder of state coffers during his nine-year presidency.
Most of the transgressions investigated by the commission involve three brothers from a wealthy Indian business family, the Guptas, who won lucrative government contracts and were allegedly allowed to choose cabinet ministers.
Zuma only testified once in July 2019.
The ANC forced Zuma — who is a member of the country’s numerically dominant Zulu ethnic group — to resign in 2018 after mounting graft scandals.