TOKYO — Japan decided on Thursday to expand its coronavirus disease 2019 (COVID-19) emergency restrictions to cover more than 70% of the population, as a surge in cases strains the medical system in the Olympics host city Tokyo and elsewhere.  

Coronavirus infections are rising faster than ever as new cases hit record highs in Tokyo, overshadowing the July 23–Aug. 8 Olympics and fueling doubts over Prime Minister Yoshihide Suga’s handling of the pandemic.  

Mr. Suga announced the new steps as new daily cases in Tokyo were set to top 5,000 for the first time and advisors to the capital said the figure could double in two weeks at the current rate, NHK public TV reported  

“New infections are rising at an unprecedentedly fast pace,” Economy Minister Yasutoshi Nishimura told a panel of experts, where he proposed “quasi-emergency” steps for eight more of Japan’s 47 prefectures.  

“The situation on the ground [at hospitals] is extremely severe,” Mr. Nishimura added, noting that serious cases had doubled in the past two weeks.  

The panel signed off on the proposal, but Mr. Nishimura told a news conference some members had warned the situation was severe enough to require a nationwide state of emergency — a stance shared by the head of the Japan Medical Association.  

Six prefectures including Tokyo are already under full states of emergency to last through Aug. 31. Another five are under less strict directives, meaning just over half the population is covered by some restrictions.  

The latest steps, to take effect from Sunday, mean that more than 70% of the population will be under some form of restriction. Criticism of Mr. Suga, his ratings already at record lows, is growing over his handling of the pandemic.  

The government says the Olympics has not caused the latest surge but experts say holding the Games now has sent a mixed message to an already weary public about the need to stay home.  

Games organizers on Thursday reported 31 new Games-related COVID-19 cases, bringing the total since July 1 to 353.  

It remains to be seen whether the latest COVID-19 restrictions, which are mostly voluntary, will have much impact as the highly transmissible Delta variant spreads.  

“I do not think that more [quasi-emergency steps] will make much difference — [it’s] simply a political statement,” said Kenji Shibuya, former director of the Institute for Population Health at King’s College London.  

The latest expansion follows a sharp backlash against Mr. Suga’s plan to limit hospitalization of COVID-19 patients to those who are seriously ill and those at risk of becoming so, while others are told to isolate at home.  

The shift is intended to address a hospital bed crunch, but critics say it will lead to an increase in deaths since the condition of patients can worsen rapidly.  

In response to calls from within and outside his ruling coalition to reverse the policy, Mr. Suga told reporters on Wednesday that the change was aimed at regions with a surge in COVID-19 cases, such as Tokyo, and was not nationally uniform.  

On Thursday, he appeared to backpedal further, saying moderately ill patients in need of oxygen treatment would be admitted to hospital.  

The backlash is a fresh blow to the premier ahead of a ruling party leadership race and general election later this year.  

Just under 31% of residents of Japan are fully vaccinated. With 15,221 deaths recorded as of Wednesday, the COVID-19 mortality rate was about 1.6%, in line with the United States. — Ami Miyazaki and Linda Sieg/Reuters