Japan is considering extending its coronavirus quasi-state of emergency in Tokyo and three adjacent prefectures, government sources said Wednesday as a rebound in COVID-19 cases has raised the possibility of the capital hosting the Olympics without spectators.

Prime Minister Yoshihide Suga's government will make a decision next week on a possible extension beyond the emergency's expiration on July 11, just before the Summer Games open on July 23, the sources said. Some in the government speculate Suga may declare another state of emergency in the Tokyo area.

A coronavirus antigen test is conducted on an experimental basis in Tokyo's Kabukicho nightlife district on June 30, 2021, for bar and restaurant employees and customers, as virus infections are on the rise in the Japanese capital. (Kyodo) ==Kyodo

Earlier Wednesday, the Tokyo metropolitan government reported 714 new daily coronavirus cases, reflecting a sharp rebound in the 10 days since the capital exited a state of emergency and shifted to quasi-emergency measures.

Tokyo's seven-day rolling average of infections per day came to 508.4, topping the 500 mark and hitting Stage 4, the worst level on the government's four-point scale.

"The number of new infections in Tokyo is on a rising trend," Suga said at a ministerial meeting on COVID-19. "We will closely monitor the situation and take necessary measures in a timely manner."

The Suga government "could consider issuing (another) declaration," a government source said.

The government has currently invoked the COVID-19 quasi-state of emergency in Tokyo and three neighboring prefectures of Kanagawa, Saitama and Chiba, as well as six other prefectures including Osaka, Kyoto and Aichi.

Under the quasi-state of emergency, which currently is set to end on July 11, alcohol can be served until 7 p.m. as long as certain COVID-19 precautions are in place, but dining establishments are asked to close by 8 p.m.

The Tokyo metropolitan government has said it will request eateries stop serving alcohol immediately if situations equivalent to Stage 4 are in sight.

At a separate meeting Wednesday of a panel of the health ministry, the National Institute of Infectious Diseases said the Delta coronavirus variant, first detected in India, accounted for an estimated 30 percent of infections in Tokyo and neighboring prefectures at the end of June.

The institute warned the figure could exceed 50 percent in mid-July.

People wearing face masks walk in Tokyo's Shinjuku district on June 30, 2021. (Kyodo)

Elderly people accounted for the lowest percentage of infections since last fall, it said, suggesting the effectiveness of vaccination.

Norihisa Tamura, minister of health, labor and welfare, has called for a discussion on how to address rising bed occupancy rates at hospitals in the capital.

Meanwhile, Suga said new applications for COVID-19 vaccine doses to be administered at workplaces and universities would remain suspended indefinitely, with the government continuing to process applications already received.

Tokyo logged 12,979 new infections in June. While cases fell in the first half of the month when the state of emergency was in place, they began to rebound quickly after measures were eased on June 21.