Tokyo's hospitals are struggling to provide routine care because of a sharp spike in coronavirus cases, officials warned Thursday as new infections in the Japanese capital hit another record high.

The city, which is preparing to host the virus-postponed Olympics next summer, raised its alert level for pressure on medical services to the top of a four-tier Covid-19 warning system for the first time.

"We need to have a sense of crisis more than ever... the virus does not have a calendar. It can strike at any time," Governor Yuriko Koike said.

Japan has so far avoided imposing strict lockdown measures and has seen a smaller outbreak than many other countries, with only around 187,000 infections and 2,700 deaths recorded overall.

But with cases on the rise, this week Prime Minister Yoshihide Suga urged citizens to reconsider holiday travel, and suspended a controversial domestic tourism campaign.

Japan has so far avoided imposing strict lockdown measures and has seen a smaller outbreak than many other countries Japan has so far avoided imposing strict lockdown measures and has seen a smaller outbreak than many other countries Photo: AFP / CHARLY TRIBALLEAU

Tokyo logged 822 new cases on Thursday -- breaking its record for the second day running and marking a jump from around 600 per day in recent weeks.

Koike warned that the city could soon see 1,000 new cases a day if infections continue at the current pace.

"Let's overcome this severe condition at any cost," she said, calling on residents to continue avoiding non-essential outings.

Since late November, businesses serving alcohol have been asked to shut early and Tokyo residents have been encouraged to work from home, although the recommendations do not carry any enforcement mechanism.

Tokyo has two Covid-19 alert systems. The other is for the level of contagion, which was raised to the maximum level last month.

The Olympics are set to open on July 23, 2021, and Koike told AFP this week that she sees "no circumstances" under which the massive international event will be cancelled.