Kim Ok-cheol, 21, was struck by the rear view mirror of a car when he was training within the Tijuca national park in Rio and suffered scratches when he fell to the ground but did not need to be taken for treatment in hospital, police said.
"It was a minor incident with light scratches. He did not want to be taken to hospital," a spokesman for the traffic police, Jose Helio Macedo, told Reuters.
He said that police officers happened to be passing by the spot when the accident occurred. Traffic police will escort cyclists during the road race events.
The local organising committee, Rio 2016, said the accident was a minor event and Tuesday was not an official training day for cycling events.
Kim was a bronze medallist at this year's Asian championships in the team pursuit.
The men's road race even starts on Saturday.
(Reporting by Rodrigo Viga; Writing by Daniel Flynn; editing by Ken Ferris)
