Japan's government is expected to announce Thursday a new virus state of emergency running throughout the Olympics, raising the prospect of a Games with few or even no spectators, AFP reported. 

The emergency measures are far looser than the harsh lockdowns seen in some parts of the world, largely limiting alcohol sales and forcing restaurants to close early.

But they will also cap attendance at large events, a key issue with just two weeks until the pandemic-postponed Games open on July 23.

"The number of new cases continues to rise in Tokyo," Japan's minister in charge of the virus response Yasutoshi Nishimura said Thursday.

"As the movement of people increases, the more infectious Delta variant now accounts for around 30 percent of cases. This is expected to expand further," he added.

The proposed emergency, which will be made official later Thursday, will run until August 22 and will set a 5,000 spectator cap, or 50 percent venue capacity, whichever is less, Nishimura said.

Alcohol will be banned at bars and restaurants, which will have to close by 8pm, and events such as concerts and conferences will have to end by 9pm.

"We hope to contain the spread of infections by placing Tokyo under a state of emergency," he said, warning that hospitalisations were rising among people in their forties and fifties.

While Japan has so far experienced a relatively small virus outbreak, with around 14,900 deaths despite avoiding harsh lockdowns, its vaccination programme has moved comparatively slowly.

Just over 15 percent of the population is fully vaccinated so far, and there are concerns that the more infectious Delta variant could produce a new wave that might quickly overwhelm local medical resources.

The decision comes with Olympic organisers scrambling to make a final call on how many spectators, if any, can be in the stands at events.

Overseas fans have already been barred from attending, and organisers last month said they would limit local spectators to 10,000 people or 50 percent venue capacity.

News.Az