Police and N4 toll officials in a joint operation detained scores of foreign travellers on three buses in Mpumalanga on Sunday.
They are believed to be Japanese nationals.
Government, as part of its clampdown in the fight against the coronavirus, has barred people from high-risk countries from entering the country.
TRAC toll concession spokesperson Solange Soares confirmed that police had requested them to stop the buses.
“Police received information on the buses which our officials stopped at the Machadodorp toll plaza at 11:40am.” The plaza is roughly 200km from Pretoria.
“The buses, which were travelling west, were stopped as they entered the toll lanes,” she said.
Soares said that they were informed that those on board the buses were not allowed into the country.
She said the buses had eventually turned around with those aboard escorted back to Mozambique.
The tourists' nationality was not disclosed by Soares, but Johannesburg's OR Tambo International Airport said, in a tweet, that they are Japanese.
The government’s command council, which was established to deal with ways of halting the spread of Covid-19 in the country, is discussing the incident.