TOKYO, June 18 (Reuters) - Japan's top medical experts warned on Friday that holding the Olympics during the COVID-19 pandemic could increase infections, and said banning all spectators was the least risky option, setting up a possible collision with organisers.

The report, led by top health adviser Shigeru Omi, was released after Tokyo 2020's organising committee chief told the Sankei newspaper she wanted to allow up to 10,000 spectators at stadiums for the global sport extravaganza.

Japan is pushing ahead with hosting the Games, which kick off on July 23, despite worries about another surge in COVID-19 infections and strong public opposition, but organisers have banned overseas spectators.

A final decision on domestic spectators will be made at a meeting to be held as early as Monday among Tokyo 2020 organisers, the International Olympic Committee, International Paralympic Committee, Japanese government and Tokyo Metropolitan government.

"I would like it to be held with spectators. I plan to head into the five-way meeting with that in mind," the Sankei newspaper quoted Tokyo 2020 head Seiko Hashimoto as saying in an interview published late on Thursday.

Speaking at the start of an experts meeting, Hashimoto said the advice from Omi would be discussed there and inform talks among the IOC and others.

In the report, Omi's experts advised holding the Games without any spectators as the least risky option given the potential for another surge in COVID-19 infections.

Prime Minister Yoshihide Suga's government decided on Thursday to ease emergency coronavirus curbs in nine prefectures including Tokyo while keeping some "quasi-emergency" restrictions.

Omi agreed earlier this week that the number of spectators at domestic events could be raised to 10,000, but only in areas where "quasi-emergency" measures, including limiting restaurant hours, have been lifted.

PUBLIC CONCERNS

Tokyo is scheduled to be under the lesser restrictions until July 11 after the state of emergency - the third since April last year - expires for the capital on June 20.

The lifting of earlier emergencies has been followed by fresh increases in infections and strains on hospitals.

Experts worry that will happen again as people start moving around more, especially since Japan's vaccination rate is low, and say organisers must be prepared to act swiftly to ban spectators or declare another state of emergency if needed.

The report by Omi also recommended that if spectators are allowed, restrictions should be tough, including limiting them to residents of the local area.

Omi, a former World Health Organization official has become increasing outspoken about the risks the event may spread the virus. Earlier this month, he told parliament it was "not normal" to hold the Games during a pandemic.

Hiroshi Nishiura, a Kyoto University professor and epidemiology adviser on the government's pandemic response who is a signatory to the Omi recommendations, said he believed cancelling the Games would be best, but that decision was for the government and organisers.

"If the epidemic situation worsened, no spectators and cancelling the Games in the middle (of the event) should be debated," he told Reuters.

Japan's public remains concerned about the risks. A survey by NHK public TV this month showed 32% favoured a cap on spectators, 29% wanted no spectators and 31% wanted the Games to be cancelled.

Japan has not experienced the explosive outbreaks seen elsewhere but a recent surge and initially slow vaccinations rollout prompted concerns about strains on the medical system.

The country has recorded more that 776,000 cases and over 14,200 deaths, while just 15% of its population has received at least one COVID-19 vaccination.