Authorities were searching for Julius Ssekitoleko, 20, who failed to show up for a coronavirus test and was not in his hotel room.

"One member of the Ugandan delegation, which the city received as a host town, has gone missing and cannot be reached," the city of Izumisano said in a statement.

"The city is making all efforts to search for the individual. We have reported the matter to police."

The statement said Ssekitoleko was last seen shortly after midnight inside the hotel by a fellow athlete.

He failed to conduct a required PCR test by shortly after noon and the alarm was raised when he was not found in his hotel room.

Uganda's delegation arrived in Japan last month, headed for a pre-Games training camp in Izumisano, in Osaka region.

But a coach tested positive on arrival, and other delegation members were subsequently asked to self-isolate, with a second member later testing positive.

Virus cases are rising in Tokyo, which is under a state of emergency, and there is heavy scrutiny in Japan of infection risks linked to the Games.

Athletes and other Olympic participants are subject to strict rules including regular testing and limits on their movement.

The Games open in a week's time, but spectators have been barred from all events in Tokyo and surrounding areas, and will be allowed into just a handful of venues outside the capital.