Lightweight champion and Namibian national Paulos "Hitman" Moses and his trainer Nestor Tobias had left the airport in a taxi around 11am on Tuesday and were bound for Parktown.
"Our car was in the slow lane and there was a car in the fast lane driving parallel with us," Tobias was quoted as saying.
"The driver flashed something to our driver, and he stopped right on the highway. There were four guys in the other car."
Tobias said the men alighted and produced firearms.
"One said this is a robbery. We were calm. Mind you, Paulos is a policeman back home."
The gang took R12,000 cash, jewellery and cellphones, before fleeing. They were not hurt.
Police spokesman Superintendent Eugene Opperman told Sapa the police had no information on the case.
"It might have been reported but I don't have any information or comment on it."
nxila@thepub_with Schabir