About 18 percent of tickets sold in Japan for next year's coronavirus-postponed Olympics will be refunded, Tokyo 2020 organisers said Thursday, with over 3.6 million seats still reserved domestically for the Games.

A three-week refund window for domestic tickets closed November 30, and organisers said about 810,000 of the 4.45 million tickets sold in Japan would be refunded and resold at a later date.

A refund application window for Paralympics tickets bought in Japan will run from December 1-21. People who purchased tickets elsewhere in the world have been told to seek refunds from local retailers.

The Games were postponed in March in the first peacetime delay of an Olympics, and are now scheduled to start on July 23, 2021.

Organisers this week laid out a raft of safety measures they said would make it possible to hold the Games, even if the pandemic has not been brought under control.

While International Olympic Committee boss Thomas Bach has said he is "very confident" spectators will be allowed at next year's event, he has also warned full stadiums may not be possible as the pandemic rages on.

A decision on the number of spectators allowed is not expected until next spring.

Organisers have promised more reimbursements if events are cancelled, or fewer seats are available because of coronavirus safety measures.