President Cyril Ramaphosa has made the dramatic announcement of a three-week national shutdown, as part of wide-ranging interventions to combat the spread of Covid-19.
The most notable measure was the prohibition of South Africans from leaving their homes unless for essential purposes.
Ramaphosa addressed the nation from the Union Buildings in Pretoria after marathon meetings with the National Coronavirus Command Council which started on Sunday.
The lockdown will be effective from midnight on Thursday.
The army will be deployed to ensure citizens are obeying the new interventions.
Healthcare and laboratory workers, emergency personnel, security officials as well as food and hygiene production workers will be exempt. A full list of those exempt will be made public in due course.
"It is clear from the development of the disease in other countries and from our own modelling that immediate, swift and extraordinary action is required to prevent a human catastrophe of enormous proportions in our country," said Ramaphosa.
He added the country needed to urgently and dramatically escalate its response, saying the coming days would be crucial in South Africa's battle against Covid-19.
Members of the SA National Defence Force have also been deployed to assist the police to ensure the measures are adhered to.
Increased screening, contact management
On Monday, South Africa had 402 confirmed cases.
Ramaphosa declared a national state of disaster just over a week ago in a bid to stem the spread of the virus, implementing a travel ban against countries hardest hit by it and the prohibition of large gatherings, among numerous other measures.
He said the number of cases in the country had increased six-fold in about a week.
"Over the past week as we have been implementing measures, the global crisis has deepened. When I addressed the nation last Sunday there were over 160 000 confirmed cases worldwide. Today, there are over 340 000 cases across the world."
He explained the government's concerns over the burden the country's healthcare system could face, noting it would not cope with the large numbers of ill patients anticipated.
"To ensure that hospitals are not overwhelmed, a system will be put in place for centralised patient management for severe cases and decentralised primary care for mild cases," said Ramaphosa.