Japanese people have been asked to wear masks at home over the holidays in Tokyo and three surrounding prefectures.
The extra precaution was recommended for elderly people and their family members as cases rise across the country.
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"The fate of the coming year will be determined by how you spend the year-end and New Year holidays," Yuriko Koike, governor of Tokyo, said in a joint letter with other regional leaders.
She added that as the health crisis continues, the holidays cannot be an excuse for people to let their guard down. Instead of attending parties or returning to their home towns for a traditional New Year celebration, Koike urged people to remain indoors and take as many precautions as possible.
For the first time since the pandemic broke out, Tokyo raised its health alert to the highest of its four levels on Thursday, although popular shopping districts appeared to be busy once again over the weekend.
On Monday, the Japan Medical Association and eight affiliated medical organisations declared a "medical state of emergency" and called on the government to impose more stringent restrictions on travel, as well as shops and restaurants.
Prime Minister Yoshihide Suga has refused to reimpose a national state of emergency on the grounds that it would be damaging to the nation's businesses.
"We need to see the results of our coronavirus countermeasures so far", Suga said in a television interview on Monday. "I will spearhead the effort and do everything that must be done".
Despite those promises, Suga's public support rate continues to decline, with many Japanese critical of the government's handling of the crisis.
The governors' appeal coincides with infection numbers and deaths rising steeply and health authorities warning that the nation's medical facilities could buckle under the strain.
The Tokyo metropolitan government reported 563 new cases of the virus on Tuesday, up by 171 from the previous day.
Nationwide, there were 2647 new cases and 620 people listed in serious condition. The national death toll from the disease went through the 3000 threshold the same day, with more than 800 deaths so far in December alone, up sharply from 382 in November.
Tokyo and the prefectures of Hokkaido, Saitama, Chiba, Kanagawa, Aichi, Osaka and Hyogo account for more than 80 per cent of all deaths.
The total number of infections across Japan to date surpassed 200,000 on Monday, with a sharp increase in cases among the elderly of particular concern to health authorities.