TOKYO: International Olympic Committee (IOC) President Thomas Bach on Tuesday praised medical workers and volunteers for making the Tokyo Games possible amid the coronavirus pandemic and said the event would send a powerful message of "peace and solidarity".

The Games, postponed last year because of the novel coronavirus pandemic, begin on Friday but will be without spectators after Japan's decision earlier this month to leave venues empty to minimise the risk of infections.

"When Japan set out 10 years ago to bring the Olympic spirit back to Tokyo... none of us could have ever imagined the unprecedented challenges we would face," Bach said at the opening of the IOC session, with Japan's Prime Minister Yoshihide Suga present.

"We could only overcome all these challenges for the Olympic Games because throughout the past eight years we were enjoying a trustful partnership (with Japan). We could always rely on you," he said.

As COVID-19 cases rise in Tokyo, however, public concern has grown that hosting an event with tens of thousands of overseas athletes, officials and journalists could accelerate infection rates in Japan's capital and introduce variants that are more infectious or deadlier.

Japan has recorded more than 838,000 cases of COVID-19 and around 15,000 deaths. Host city Tokyo confirmed 727 cases on Monday, and the seven-day moving average was just over 1,100.

About one-third of Japan's population has had at least one vaccination shot and about 22% are fully vaccinated.

There have also been 58 cases of Olympics-related positive cases that have been recorded since athletes and officials started arriving in Japan.

Days before the opening ceremony in Tokyo, 68% of respondents in an Asahi newspaper poll this week expressed doubt about the ability of Olympic organisers to control coronavirus infections, with 55% saying they were opposed to the Games going ahead.

"We can only be together today because of the heroic efforts of all the doctors, nurses, healthcare workers and the many volunteers around the world," Bach said.

Bach said that cancelling the global sports extravaganza had never been an option for organisers.

"The IOC never abandons the athletes. Therefore, we took an unprecedented decision to postpone the Games (last year). Today I can admit we did not know how complex this would be," he said.

Suga - who has seen his support rate slide since he took office last September, largely due to his handling of the pandemic - promised organisers would implement all necessary measures to have safe Games even without spectators.

"But the significance of Tokyo will not be reduced by this," Suga said in a brief address. "Now is the time to unite."

Bach also said that World Health Organization Director-General Tedros Adhanom Ghebreyesus would be in Tokyo on Wednesday to "share his thoughts with us in a keynote speech".