Tokyo will be in a state of emergency for the Olympic Games after the Japanese government took action against rising coronavirus infection rates.

The measures are set to remain in place until August 22, a fortnight after the Games finish, Japanese agency Kyodo News reported.

The decision throws into doubt the possibility of even limited numbers of Japanese spectators attending the Games, with overseas fans having been barred in April.

"We must take stronger steps to prevent another nationwide outbreak, also considering the impact of coronavirus variants," Japanese Prime Minister Yoshihide Suga said in quotes reported by Kyodo News.

Games organisers last month put in place plans to allow venues to be 50 per cent full, up to a maximum of 10,000 people.

State of emergency rules regarding attendances are set at regional level, but the national government advice is that events with spectators should run no later than 9pm, putting a major question mark on whether fans will be allowed to attend any night sessions in Tokyo.

Tokyo 2020 chief executive Toshiro Muto has stated previously that dignitaries and VIPs would not be counted within capacity limits and would instead be classed as organisers, so may still be able to attend even if the general public cannot.

Children attending Olympic events as part of a schools programme were also exempt from the capacity caps, Muto has said.

Japan's top coronavirus advisor, Dr Shigeru Omi, had recommended to Games organisers that the best approach was to stage the event behind closed doors.

The announcement of a state of emergency coincided with the arrival in Japan of International Olympic Committee president Thomas Bach.

The decision will not deter the IOC from pressing ahead with staging the Games.

Its vice-president overseeing the Games, John Coates, said in May that the event would go ahead whether Tokyo was in a state of emergency or not.

The Games officially begin on July 23, with the closing ceremony taking place on August 8.