The number of COVID-19 patients isolating at home is sharply increasing in Tokyo amid a surge in new cases.

The number of people hospitalized with the disease topped 4,000 for the first time in the Japanese capital. About 25,000 people with less-serious or no symptoms are isolating at home.

Physicians registered with a group called FastDOCTOR are visiting patients in their homes at the Tokyo government's request.

One patient in his 20s regularly receives telephone calls from a local public health office to check his condition.

But he says he is worried that his condition may suddenly deteriorate between the calls.

Another at-home patient is a woman in her 50s. She may have developed pneumonia, but local health officials have failed over the past week to find a hospital that would accept her. Instead, a visiting doctor uses an oxygen concentrator to help her breathe easily.

The doctors have had to decline some requests for house calls when no oxygen concentrator is available. In such cases, they call ambulances for emergency aid.

Dr Kikuchi Ryo, who represents FastDOCTOR, says more at-home patients are developing pneumonia because they cannot be hospitalized.

Also, he says he is worried that the Tokyo Paralympics could prompt more people to go out and risk getting infected with the coronavirus.