Japanese authorities have reported more than 3,200 coronavirus cases so far on Thursday... the most ever.
More than 191,000 people have now tested positive in the country. Around 2,800 people have died.
A record 822 cases were reported in Tokyo on Thursday.
66 are in serious condition.
In light of that growing number, the Tokyo Metropolitan Government raised its alert for the healthcare system to the highest level - for the first time.
One of the city's expert advisors says it has become increasingly difficult to balance caring for coronavirus patients with regular medical work.
He urged officials to focus on curbing the number of new cases, in order to protect the health care system from buckling under the strain.
Inokuchi Masataka of Tokyo Medical Association said, "There's already a lot of frontline healthcare workers assigned to care for serious cases. So it's hard to assign any more. In order to accept more seriously-ill patients, we need to limit who we admit, taking into account any pre-existing conditions."
The Tokyo Governor asked residents to continue to stay home as much as possible.
Koike Yuriko said, "When you need to get essentials, please limit your time and who you go out with."
She stressed that people should be aware that the virus can be transmitted by carriers who show mild symptoms, or none at all.