Japan has been accused of covering up coronavirus cases to protect the Olympics, after a spike in Tokyo's infection count following the postponement of the Games.

The Japanese government insisted for weeks that Tokyo 2020 would go ahead as planned, but finally gave in last week and postponed the Games until 2021.

Since then, Tokyo's daily infection count has risen from 16 to 63.

Former Japanese prime minister Yukio Hatoyama is among those voicing the suspicion that Tokyo's numbers are rising because Japan now has no reason to hide them.

Commuters walk out of a Tokyo railway station today, after the Japanese capital recorded a spike in cases shortly after postponing the Olympics

'In order to make an impression that the city was taking control of the coronavirus, Tokyo avoided making strict requests and made the number of patients look smaller,' the former PM alleged.

'The coronavirus has spread while they waited. [For Tokyo governor Yuriko Koike] it was Olympics first, not Tokyo's residents.

Current PM Shinzo Abe agreed to postpone the Games in a phone call with International Olympic Committee chief Thomas Bach last Tuesday.

A day later, governor Koike asked Tokyo residents to stay home at weekends until mid-April, saying cases had shot up to 41 in a day from 16 earlier in the week.

On Saturday, Tokyo reported 63 new cases, another single-day record.

The governor said that infections in Tokyo were on the brink of an explosive increase, and that stronger measures, including a lockdown, could be needed if the spread of the virus doesn't slow.

'Is this just a coincidence?' Maiko Tajima, an opposition lawmaker said during a parliamentary session last Wednesday, citing Tokyo's sudden spike.

However, health minister Katsunobu Kato said there is 'absolutely no relationship' between the Olympic postponement and the number of confirmed cases.

Prime minister Abe said: 'I'm aware that some people suspect Japan is hiding the numbers, but I believe that's not true.

'If there is a cover-up, it will show up in the number of deaths.'

Abe cited experts as saying a big reason for the recent rise is the growing number of cases that cannot be linked and a jump in infections from abroad.

The prime minister told people to 'be prepared for a long battle'.

A woman wearing a protective face mask walks past the Olympic rings in front of the Japan Olympics Museum in Tokyo today

Japanese prime minister Shinzo Abe, pictured during a virtual G20 summit last week, has denied claims of a cover-up

Experts have found a rise of untraceable cases in Tokyo, Osaka and other urban areas - a sign of an explosive increase in infections.

Abe said on Saturday that Japan is now on the brink of a huge jump in cases as it becomes increasingly difficult to trace and keep clusters under control.

'Once infections overshoot, our strategy… will instantly fall apart,' Mr Abe warned. 'Under the current situation, we are just barely holding up.'

He said a state of emergency is not needed just yet, but that Japan could at any time face a situation as bad as in the United States or Europe.

Abe has convened a new task force under a recently enacted special law that would allow him to declare a state of emergency in specific areas, including Tokyo.

Japan's strategy has been to focus on clusters and trace infection routes rather than testing everyone.

Experts set a high bar for testing eligibility, allowing them only for those linked to clusters or those with symptoms, because they fear massive testing will fill up beds that are needed for patients in severe need.

From February 18 to March 27, Japan tested about 50,000 people, a daily average of 1,270.

South Korea, by contrast, had tested about 250,000 people by mid-March.

As of Sunday, Japan had 2,578 confirmed cases, including 712 from the Diamond Princess cruise ship, with 64 deaths, according to the health ministry.