A top Japanese virologist and government adviser has warned of the risks of spreading Covid-19 infections during the Tokyo Olympics, the Times of London reported, the latest high profile caveat about the global sporting showpiece.

Tohoku University professor Hiroshi Oshitani was an architect of Japan's “Three Cs" approach to the pandemic, which advises avoiding closed spaces, crowds and close contact situations, Reuters reports.

"The government and the organising committee, including the International Olympic Committee, keep saying they're holding a safe Olympics. But everybody knows there is a risk. Its 100 per cent impossible to have an Olympics with zero risk [...] of the spread of infection in Japan and also in other countries after the Olympics,” the Times quoted Oshitani as telling the newspaper.

“There are a number of countries that do not have many cases, and a number that don't have any variants. We should not make the Olympics (an occasion) to spread the virus to these countries,” he added, noting most countries lack vaccines.