South Africans arriving home from high-risk countries will have to be quarantined for 14 days, President Cyril Ramaphosa announced on Monday.
The travel restrictions were announced as part of a nationwide lockdown that will take effect on Thursday.
The lockdown includes several measures that will be implemented to combat the spread of Covid-19 to "flatten the curve".
The restrictions will have an impact on South Africans and travellers arriving from high-risk countries.
"South African citizens and residents arriving from high-risk countries will automatically be placed under quarantine for 14 days," Ramaphosa said.
Non-South Africans returning from high-risk countries would not be allowed entry, he added.
"Non-South Africans arriving on flights from high-risk countries that we prohibited a week ago will be turned back."
Those already in the country will also be subjected to a 14-day quarantine period.
"International travellers, who arrived in South Africa after 9 March 2020 from high-risk countries, will be confined to their hotels until they have completed a 14-day period of quarantine," Ramaphosa said.
Additionally, flights to Lanseria Airport in Gauteng will be suspended.
The restrictions follow a decision by the National Coronavirus Command Council to enforce a nationwide lockdown for 21 days.
"This is a decisive measure to save millions of South Africans from infection and save the lives of hundreds of thousands of people.
"While this measure will have a considerable impact on people's livelihoods, on the life of our society and on our economy, the human cost of delaying this action would be far, far greater," Ramaphosa said.