The SANDF has been deployed to support police during the 21-day lockdown.
CAPE TOWN - Officials identified quarantine sites across the country on Wednesday as the number of confirmed coronavirus cases rose to 709.
Health Minister Zweli Mkhize warned infections were expected to keep rising.
South Africa has reported the most coronavirus cases in sub-Saharan Africa, and public health experts are worried that the virus could overwhelm the health system if infection rates rise steeply.
Public Works Minister Patricia de Lille told a news conference that her ministry had identified more than 16,000 beds in potential quarantine facilities, including government buildings, hotels, holiday properties and hospitals.
De Lille's spokeswoman and a Health Ministry spokesman were not able to say who would be placed in the quarantine sites.
President Cyril Ramaphosa has been praised for ordering some of the toughest measures on the continent to try to halt the spread of the virus, including a 21-day lockdown from midnight on Thursday, deploying the army to support police and ordering underground mines to suspend operations.
Businesses of all sizes are bracing for a big impact from the lockdown, with Airlink becoming the latest local airline to suspend flights from midnight on Thursday and state power utility Eskom applying for its critical staff to be exempt so that electricity supplies can continue uninterrupted.
South African National Parks said it would close all its tourism facilities to the public from Wednesday.
Mining Minister Gwede Mantashe said production of gold, chrome, manganese and other minerals would be scaled down but that the processing of platinum group metals would continue.
The South African Reserve Bank (SARB) launched a bond-buying programme, giving into public and political pressure to intervene more directly in providing stimulus.