The public will be asked not to line the route of the Olympic marathon over fears that crowds of fans could spread the coronavirus, Tokyo 2020 organizers said Tuesday.
With less than three weeks before the pandemic-postponed Games begin, concern is growing over a rebound in virus cases in Japan.
"In view of the current Covid-19 situation, it will be necessary to reduce the risk of infection by restricting the movement of members of the public," organizers said in a statement about the marathon and race walk events.
"It has therefore been decided to ask the public to refrain from spectating along the course," they said.
The marathon was at the center of controversy in the original build-up to the 2020 Games, when it was moved to northern Sapporo from Tokyo to avoid the capital's punishing summer heat.
Organizers said they had met police and local government officials to discuss arrangements for the women's and men's marathons, which will take place on August 7 and 8, and race walk events.
The statement said they would continue to work with local officials "to ensure a safe and secure Tokyo 2020 Games for all participants and for the citizens of Sapporo and Hokkaido".
Japan's government is this week expected to extend current virus restrictions, which limit spectators at sports events to 5,000 and limit the opening hours of bars and restaurants, in several parts of the country.
Japan's Covid-19 outbreak has not been as severe as in some countries, with around 14,800 deaths, but experts say another wave could stretch medical services as the Olympics begin.