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.

But the government has been reticent to take measures that could send the economy back into reverse, soon after it exited a recession.

However, Suga 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.

- Vaccination plan -

Japan imposed a first state of emergency in spring, allowing local governors to call on businesses to close and to request people to stay at home.

The measure carries no penalties for non-compliance, but the requests were widely observed this spring.

The scope of any new emergency remains unclear, though the Nikkei daily reported the government would not seek school closures. Suga said "limited and focused measures" would be effective, without specifying further.

Local media reported the measure could begin from Saturday, but there was no immediate confirmation.

The coronavirus outbreak has been more contained in Japan than some other countries, with just over 3,500 deaths since the first domestic case in January.

With no legal mechanism to enforce business closures or stay-at-home orders, Japan has avoided the harsh lockdowns seen elsewhere.

Suga said the government was expecting vaccine data from US companies by late January, and vaccinations could begin by late February.

"Initially, we wish to start vaccination of medical workers, the elderly and those who work at elderly care facilities," he said.

"I will also take the lead in getting vaccinated," he added, in an apparent attempt to bolster confidence in a country where vaccine hesitancy is comparatively strong.

The new spike in infections comes little more than six months before Tokyo is set to host the virus-delayed Olympic Games.

Tokyo 2020 was postponed last spring as the scale of the pandemic became clear, but despite optimism from officials and organisers, polls show most Japanese oppose holding the Games this summer, favouring a further delay or outright cancellation.