A member of the Nigerian Tokyo Olympics delegation became the first Olympics visitor admitted to hospital with COVID-19, Japan's TV Asahi reported on Friday, as Japan battles to stem rising local infections with the Games a week away.

The person, a non-athlete in their 60s, tested positive on Thursday evening at the airport and had only mild symptoms but was hospitalised because of their age and pre-existing conditions, TV Asahi said, without giving further details.

Earlier in the day, the Australian Olympic Committee said that Australian tennis player Alex de Minaur, ranked 15th in the world, had tested positive for COVID-19 prior to his departure for the Tokyo Olympics, the latest athlete to see his Olympics dream shattered by the virus.

READ: Tokyo's Covid-hit Olympics in numbers

U.S. basketball star Bradley Beal’s Olympic dream was cut abruptly short on Thursday when USA Basketball announced the Washington Wizards star will miss the Tokyo Games after he entered coronavirus protocols at the training camp in Las Vegas.

Several COVID-19 cases have emerged involving athletes and others involved with the Games, which start July 23, even as infections spread in Tokyo and experts warn worse may lie ahead.

Tokyo is under a state of emergency for the pandemic, but most steps to curb its spread are voluntary and many people say they have grown weary of complying.