Japan's Prime Minister Yoshihide Suga said Monday he was considering declaring a state of emergency in the greater Tokyo area over a "very severe" third wave of coronavirus infections.

Speaking at a regular New Year press conference, Suga also said he hoped vaccinations would begin in Japan in late February, adding that he would be among the first to receive one.

He urged people to avoid non-essential outings and said the government would introduce legislation to penalise businesses that flout requests to shorten hours or close, as well as provide incentives to those who abide by such calls.

Suga also insisted the government was still committed to holding the virus-postponed Tokyo 2020 Olympics this summer, saying the Games would be "proof that mankind overcame the virus".

Suga, who took office in September, has faced increasing pressure over his government's response to record numbers of new infections.

Tokyo on Monday recorded 884 new infections and said the number of serious cases -- those on a ventilator or ECMO machine -- rose to a record 108.

On Saturday, Tokyo governor Yuriko Koike, joined by governors from three neighbouring regions, called on the central government to impose a state of emergency in their areas.

Koike on Monday warned that "we have already entered an unprecedented state of infections," and called on people to avoid non-essential trips after 8:00 pm.

She said she would not seek to close schools but urged businesses serving alcohol to close by 8:00 pm from Friday, and asked all restaurants to shut by that time from January 12.

Suga's government has been reticent to take measures that could send the economy back into reverse, soon after it exited a recession, but the prime minister said Monday he realised "a stronger message was necessary".

"The national government will consider issuing a state of emergency," he said, adding that it would prioritise measures to reduce infection risks from drinking and dining.

Opposition politicians criticized the move as overdue, with Constitutional Democratic Party leader Yukio Edano telling reporters his party had been "calling on the government to declare a state of emergency since mid-December" while referring to the delay in action as "very regrettable", according to Japan's Jiji news agency.